Assuming the '97 is like my '95...
1. Remove U-shaped trim ring, it just pops off.
2. Remove the four 10mm bolts.
3. At this point, the radio is loose, just pull it out and remove the wiring attached to the back. Remove the bracket that is attached to the radio, you'll need to attach that to the new radio. The bracket is held on by two or four phillips head screws (small ones), easy.
That's it. This was by far the easiest radio removal I've done over the years.
Here's a picture of the radio I put into my car, it's a Sony GT410U. The orange light is from the flash drive I have plugged into the front of it.