There is only one place in Washington State that can truly upgrade a stereo without drilling any holes or cutting any wires, or anything. If they remove the stereo there will be absolutely no indication that there was ever an aftermarket stereo. Obviously, this comes with a price. The place is Innovative Audio in Bellevue. They are the most amazing stereo shop I've ever seen.

If IA is out of your league, I think the next best bet is Magnolia Hi-Fi...with the Roosevelt and Bellevue location probably being your best bet.

I would avoid any of the other stereo shops in the area for installation work. I like Stereotomy in Issaquah because they carry Eclipse and some other good stuff, but I've seen several severe hack jobs come out of their installation bay...two of them being on my own vehicle.