Disconnect Battery First!

Remove your HVAC trim panel by firmly gripping the panel and pulling toward
you. It will pop off to reveal a #2 Phillips screw next to an alignment post
in the lower right corner of the large radio/center vent trim panel.
Remove this screw, and then remove the upper trim panel by pulling it
directly rearward. BE careful, the Bose faceplate may stick to it and pop
off along with the trim panel, but can be easily reinstalled. You can now
remove the Phillips screws holding the radio to the car.

I just did this.  Wanting a CD player I bought an OEM on ebay then
found it didn't play mp3's bummer.  Anyway it was a nice unit.  To
remove the radio from my 1995 Altima I had to pry the plastic from
around the console shift lever.  It snaps in.  next a screw near the
hood release lever then another toward the console at the same level.
Remove that panel, it snaps in along the top.  Now remove two screws
behind the shift, two in front of the shift and two above the radio.
You should be able to remove the facade now.  The radio frame is held
in by four screws.  Removing those you take out the radio down to the
coffee cup holder.  Unclip the connectors and the take out the 4 screws
holding the radio and you're done.

I went and bought a Sony but have met disappointment in that it extends
into the car though it plays well.  It doesn't look bad and I got
around the faceplate issue using hotglue but when I put a bottle of
water or cup of coffee in the holder it hits the knob or elsewhere on
the radio.

Bill