I am working on sorting and writing up captions to some actual installation pictures from my install in my ’08 Legacy, as well as pictures from other installs.
For now, here is an electronic “How-To” from an online vendor. It should help get you started:
http://carstereoadapters.com/wp-content/uploads/2012/01/2005-2009-Legacy-Master-Sheet.pdf
Credit for photos and some text to deneb on LegacyGT.com
1) Using a flathead screwdriver or similar tool, pry off the door handle cover. Pry down and out, this is easily the most difficult part of removing the door panel. Once you get the cover out a little ways, you may want to stick the pry tool down into the space created to get more leverage. There are three clips that hold the cover onto the handle. Many people break one or more of the tabs if they are not careful, but it didn’t seem to make any difference when reassembling the door panel.
2) Using a phillips head screwdriver, remove the two screws that secure the door panel to the door. Picture shows the location of the upper screw, the lower is easily visible.
3) Using a flat head screwdriver or small pry tool, pry out the cover behind the door latch. Remove the screw.
4) Pry off the cover at the top of the door where the door meets the A pillar
5) Remove the door panel. There are several clips that secure the door panel to the door, these pry off fairly easily (or rather, the panel pops off pretty easily as you pry it off from the door. I was able to do this just using my hands and no other tools). Remove the wiring harnesses and door locking cables. Picture shows the door after the panel is removed.
6) Door panel, once it has been removed.
You will need Metra 72-8104 wiring adapters for the front and Metra 72-9300 or 72-9301 adapters for the rear. See http://carstereoadapters.com/tools-and-how-to/wiring for info about the 9300 v. 9301 wiring. Either will work but may require swapping connectors.