Inspired by wing_woo's excellent post
on installing a Homelink unit in his 2009, I decided to try the same project with my 2008. Searching on Ebay found hundreds of these units pulled from many different makes. There are many different styles and colors, but internally they are pretty much the same. I was looking for a gray unit and found one that looked a little different than the rest as it had numbered buttons which turned out to be lighted!
Got this one for $15.50! It was originally installed in a Volvo. I pretty much just followed wing_woo's instructions which worked out well. Since I don't have a sunroof, I tapped into the wiring going to my autodimming mirror, since the wires were right there. The scariest part is taking the X-acto knife to the headliner to cut the hole, but it was easier than I thought. To keep the headliner from flexing when pushing a button, I backed up the transmitter with a piece of styrofoam wedged nicely between the unit and the roof. Took me about an hour this morning and here is how it turned out:
BTW, the LED's in the unit were green, but I replaced them with amber for obvious reasons!