I like inthewoods' method (mainly because it's cheap at <$10 and effective), so bought the same LED strip and he was kind enough to send me one of the bulb adapters. I finally got some time this morning, so gave it a shot. Total project took me two hours, including a trip to the hardware store and a couple of screw-ups. Here's how it went:
Removing bulb casing is a snap. Removing bulb is only a little tricky (had to figure out to carefully pry off sides of metal casing in order to remove).
Replace bulb with bulb adaptor.
At that point I tested the strip by touching the wires to the bulb adaptor--success!
Here's where it actually got a bit tricky: the bulb adaptor has pretty short wires attached, and I didn't have the female connector that would match the included male connector. So I removed the male connector and soldered the wires to 18 gauge wire (smaller wire would be better, but it was on clearance at Ace Hardware). Then I had to fit the soldered connections INSIDE the metal casing, since the adaptor wires were too short to run outside the casing. I spent ~20 minutes fumbling around because the bulb adaptor kept popping out when I squeezed everything together. Finally got it all right though, and from there it was easy again.
Taking the 18 gauge wire, I passed it through the hole in the liner for the bulb housing, the up to above the wheel well. This part was surprisingly easy due to the presence of an access panel half way along the run.
Then I just had to place the LED strip using the self-adhesive 3M backing, and connect the wires to the 18 gauge using screw connectors (didn't want to solder in my trunk, and figure that it'll be sturdy enough).
If I can figure out how to include pictures, I'll attach some. But the bottom line is, anyone who has a few tools and is a little bit handy can do this mod in a couple of hours. If you're not thrilled about stripping wires and/or soldering, I'd spend $10-$20 more for deautokey's solution. Either way, the added light is awesome!