replacing the car computer is like swapping out a hard drive on your home computer.
For $700, I'd go to a local wrecker and get one off them for maybe $50 or so.
You'll need a small wrench, or screwdriver and pliers to pull the old one out.
On my /94 its under the hood on the left (passenger side) at the front. It looks like a metal box with some big plugs on the side that the wiring harness connects to.
Here's a video showing someone installing a PCM (car computer) in a Chrysler.
Removing a PCM:
http://www.youtube.com/watch?v=jT8ZiLYydKM&NR=1
Installing a new PCM:
http://www.youtube.com/watch?v=DCpZHICcWAA