How do you install a CD player into a 97 Geo Metro?

If I'm not mistaken there are four screws in the casing where the current stock stereo is that need to be removed. Two on top and two on bottom. You'll see them if you hold you head down low and look up.

When you buy the new stereo you should make sure that you also get the adapter for that make and model of car. It should be as simple as unclip the old and reclip the new. Just make sure that the wires match color and position. If not you may have to make a few snips and use some electrical tape, but I don't think that should be the case.

Mine was already in when I bought the car so I'm not sure exactly about the procedure, but I've had to take it out to fix the wiring to the rear speakers and it wasn't very difficult.