If the 2000 Legacy is anything like my 1995 Legacy removing the trim around the radio can be quite amusing. In my legacy, I had to pull out the cup holder above the radio and remove the screw on either side to remove the cup holder. Then, I had to lift the center arm rest cover and remove two screws from there. That releases the cover around the parking brake which then releases the cover around the shifter. Finally if you pull out and remove the ashtray there is one or two screws that need removed from there. After all of that, you should be able to remove the trim and get to the radio. Once replacing the radio, we had to cut away some of the trim to fit around the new radio. My trim literally sits against the trim around the face place, to the point that remove the face plate from the radio makes it difficult to replace it so I just leave my face plate on. I figure there is only one way that radio is coming out and if someone wants to go through all the hassle of removing the trim to get to the radio... they can darn thing.
Also, not sure if you are replacing the radio to update or because the current one stopped working. If it is because the current one stopped working, which is why I replaced mine, be aware (as we found out after the fact) there is a fuse in the fuse box under the steering wheel AND there is a fuse for the radio in the fuse box under the hood. Had we known about the fuse under the hood in the beginning, I more than likely wouldnt have needed the new radio.
Hope that helps.