These rubber "accordians" can crack over time. Fortunately the rubber piece is only around $60, and can be replaced easily. You'll need to set aside about an hour and a half if you haven't done this before.
Tools needed:
Flat-bladed screwdriver
4mm allen wrench
Ratchet with short extension and 10mm socket
Parts needed:
The bellows
Two plastic expanding fasteners (might come with the bellows)
First, deploy your spoiler manually, and shut off the ingnition. No need to disconnect the battery.
You will see, along the rear edge, four caps, as seen below. These pry out easily with your fingers or with a flat bladed screwdriver. No paint to worry about, just try not to mar the plastic.
With the caps off you can access the 4mm allen head bolts:
I found these to be a bit tight due to exposure to the elements, but I was able to get them off with an allen key. A long allen socket would work better.
Once the bolts are out, the top tray (painted part) of the spoiler can be slid toward the rear and off. Put it somewhere where it won't be scratched.
Now you can see the fasteners holding the top of the bellows to the spoiler. There are two explanding plastic fasteners, one on each corner, and several sliding hooks. I destroyed my plastic fasteners since my new bellows came with new ones. Just nipped them off with wire cutters.
With the two plastic fasteners off you can disengage the hooks and detach the top of the bellows by sliding it to the right, and down. The top edge of the bellows is actually sandwiched between a long metal strip and the spoiler. The metal strip has the hooks that go through pre-cut holes in the bellows.
View from below:
With top of bellows detached:
With the top of the bellows detached, open the engine lid. You will see several circular clips holding the bottom of the bellows to the engine lid:
There is one under the fan, so you will have to detach the fan. Just three 10mm bolts. Just let it hang by the cable, out of your way. Be careful not to scratch your paint while removing the clips. In my case, the clips themselves had scratched the paint a bit. Fortunately this is one of the body areas that receives only a "rough" paint job from the factory anyway. Save those clips. It is not necessary to replace them.
With the clips removed, you can pull the bellows out.
As with the top, there is another frame piece running the length of the bottom of the bellows. This sandwiches the bottom of the bellows to the engine lid. The bellows has pre-cut holes for the nubs on the metal strip:
Lay your old bellows alongside you new one, so that you can see how the top and bottom frame strips fit.
Reassembly:
Transfer your frame pieces to your new bellows.
Then attach bottom of bellows to engine lid with the circular clips. Push those numbs through and get those clips up as tight as possible. The idea is to clamp onto the lower bellows edge.
Re-attach the fan.
Close engine lid
Make sure the top frame piece hooks are threaded through the top of the bellows, push up through the corresponding holes in the spoiler, and slide to the left to secure. Make sure all of the hooks are engaged and snug. Then insert and secure the two plastic expanding fasteners in the corners. This step will confirm that you have the bellows and the spoiler snug and aligned properly.
Now grab your painted spoiler top, and look under it to make sure the locking tabs are lined up. Push down, and slide toward the front of the car to lock the tabs. The top and bottom of the spoiler should mate very well. If you feel gaps around any edges, check and adjust.
Finally, secure the top of the spoiler with the four allen screws. Put the plastic caps on, and manually raise and lower the spoiler to make sure you haven't left any tools in there...