The factory aerokit comes with everything you need to install.  You should get the following pieces:
Front bumper cover
Rear spoiler and decklid
Left side skirt
Right side skirt
Rear decklid wiring harness
Associated hardware
Additionally, you can get the GT trim extensions for the rear bumper cover.  These are separate from the factory aerokit.

Before you get started:
Read and re-read the Porsche TSB several times to familiarize yourself with what you will be doing.  This really helps.  Take your time, there isn’t any awards for a quick job and your work will more likely be better if you just relax and go at your own pace.

Download the Porsche TSB PDF file here, there are two locations from where you can download this file, if one is busy try the other.  The file is a very large file 4588kb, so it may take some time to download.
 
 
 

You don’t need to jack up the car for any of these installations; however, it may make a few of them easier.  I had the car on the ground the whole time and did not remove the wheels (wheels were removed after the install to take a few pics for this DIY).

Tools needed
High Quality #2 Phillips Screwdriver (Snap-On or Craftsman Professional)
High Quality #2 Phillips “Stubby” Screwdriver
Small straight blade screwdriver
Good quality “dykes”
10mm socket and ratchet (1/4” and 3/8” drives)
Variable speed drill w/ various high quality bits and #2 phillips bit
Measuring tape 
8-12 good quality beers

Some notes about buying used pieces:
If you decide to save a little money and get some or all of the aerokit pieces used, it would definitely benefit your pocketbook to get the pieces from someone that has the same color car as yours.  I purchased the front bumper cover and rear spoiler used, but any money that I saved was just about spent in having to prep the pieces for the different paint color.  I’m not going to get into the discussion on paint prep, but in my case, it made a big difference.

Paintwork:
I left this up to the professionals.  My town (Knoxville, TN) does not have a large variety of body shops, so I did what little research I could and found that using the Porsche dealer’s recommendations was probably the best.  The paint used was “Glassurit”, similar to the factory Porsche paint.  Another recommended brand would be Sikkens, but no one in Knoxville is qualified to spray this type of paint.  Bummer.

Starting the job:
After picking up the pieces from the body shop, I had to decide where I was going to start.  The front end seemed the likely candidate, so I began to read (and re-read) the instructions found in Porsche TSB 3/00 from July of 2000.  It is pretty clear, but there are a few tricks to getting the bumper cover off easily.

First, remove the headlights.  The procedure for this can be found in the owner’s manual.

Next remove the plastic cover from around the hood release latch.

Remove the two screws securing the bumper cover to the car under the removed plastic cover.

Remove the side marker lights.  They just pull out.  If you have a hard time, use a small screwdriver (carefully) to push in the metal clip holding it back.

Remove the screw (one) from the bumper cover that was being covered by the side marker.

Now for the “booger” screw.  There is a Phillips screw that runs perpendicular to the ground behind the marker light.  To access it, you need to remove the plastic retainers holding the wheel well liners in place (you don’t have to remove the whole liner).  Once a few of these are removed, you can push the liner out of the way and gain access to this “booger” screw.  It is highlighted in the exploded diagram.

Once this screw is out, remove the “mudflaps” at the rear sides of the bumper cover, just in front of the wheels. Under each flap is a screw holding the corners of the bumper cover to the car.  Remove them.  Then remove the six or seven screws holding the bottom of the bumper cover to the front support.  With all of the screws removed, pull forward and bumper cover will easily come off.  If it doesn’t come easy, STOP.  You missed a screw somewhere. 

Once the bumper cover is off, take the time and vacuum the radiator intake areas.  Mine were filled with road debris including leaves, bugs, cigarette butts, etc.  This procedure made a noticeable improvement in the cooling readings. 

You will need to transfer a couple of screw backing plates from the old bumper cover to the new one.

Installation is the reverse of removal.  Make sure to put all of the screws back in.  You will not use some of the mud flaps with the aerokit, so these will be left over.
 

Rear Spoiler and Deck Lid:
Replacement of the decklid is very straightforward. 

Begin by removing the existing decklid.  Locate the wiring harness just inside the right (passenger) quarter panel and disconnecting it. 

Remove the bolts holding the decklid to the hinges and remove the decklid.

Remove the three bolts from the fan/light assembly.

Remove the fan/light assembly and disconnect the wiring harness from it.
Remove the rubber stops from the bottom of the decklid as well as the rubber weather strip from the decklid.

Transfer all of these pieces to the new decklid.

Mount the new decklid.

The list of transferred parts are shown as:

1 - Rubber bumper stops
2 – Decklid latch
3 – Weather Strip
4 – Air snorkel
5 – Fan/light assembly
6 – Aerokit wiring harness

I started with the alignment of the lid at the same place where the original one started.  Mine was close, but I needed to make some minor adjustments.  This is where a second set of hands would come in useful.  Loosen the bolts just a bit to move the decklid around until the optimal fitment is achieved.  Be careful that the new wing does not hit the body when the decklid is open.  Mine has about a ¼” gap.  If the lid is raised quickly, the springing action will make the wing hit the body and possibly mar the surfaces.

If you’re lucky (I wasn’t), then the lid will fit fine and the latch will close and open correctly.  Closing is not so much of a big deal, but upon opening, you need to let the latch spring the lid up a bit (you hear a slight “click” when you operate the latch).  By loosening the two 10mm bolts that secure the latch, you can re-position so that it closes and open properly.  This part is trial and error.  In no case should the decklid close and not be able to be reopened.  The worst that will happen is that you will have to call your wife (or someone you trust) to hold the decklid release lever (or button) while you pull up on the lid.
 
 

Side Skirts Installation:

Follow the TSB instructions very carefully.  The most critical part (in my opinion) is the placement of the templates on the car so that the aluminum bracket is mounted properly.

You must use the Porsche self-tapping screws.  Don’t ask me why, but that’s what it says in the TSB.  These are a bugger to get in.  I gave up on the battery-powered drill and broke out the heavy duty Makita electric and had to push pretty hard.  Once they break through the metal, they snug down easily.

Figure 6 Fitment of Side Skirt at Front Wheel Well
 

Figure 7 Fitment of Side Skirt on Rear Wheel Well

I really don’t have too much more advice on this part since it is covered quite well in the TSB.

Rear GT Trim Pieces:

These were very easy to install.  Simply tape the template to the rear bumper cover (there are alignment points on the template) and drill the holes in your rear bumper cover.

I removed several rear bumper cover mounting screws and just pulled the cover far away from the body to install the trim pieces. 

Left over pieces.  Once you have completed the installation of the aerokit, you will have several pieces of Porsche left over.  The major pieces being the front bumper cover and the rear decklid.  In addition, you will have some mounting hardware, the side skirt templates and the mudflaps from the car as left over.  I have enclosed a picture fo the leftover mudflaps.

You have now completed the installation of your new aerokit.

Break open the beer…… 

Enjoy!