A while back, I took the door panels off to install new speakers. It's really easy. It's not that much different than the 2nd generation Legacy.
I'm writing this from memory, so it might not be 100% accurate.
Remove the tweeter covers if you have them. Pry off the panel surrounding the window switches. Pry off the plastic "button" covers on the door handle and on the arm rest. You'll see the screws that need to be removed. After removing them, gently pry the panel starting at the bottom. It should come off without too much force. When you get to the top, push the whole panel upward, and it should come right off.
Once you start feeling your way around, you'll see how easy it is.
Hope this helps.