While I'm not trying to brag, I am one of those mentioned above that know a thing or two about this system. I have a little cottage business refurbing these systems, and I have a few happy customers here on FCBO.
I can repair the dash dial (most are broken) and refurb the underhood servo, as well as cosmetically detail the rest of the system. While it's not cheap, you get a nice product that works.
When you're getting the parts from a donor vehicle, be aware that there are very specific parts you need to have, or the system can't be made to work. In addition to the dash dial and underhood servo, you need the brake pedal switch and the gas pedal assembly, as both are specific to the Autopilot system. You should have a template of the cutout in the floor under the gas pedal from the donor car so as to properly install it in your car. There is a specific wiring harness and bowden cable that is part of the system. The rest are the mounting brackets for the servo.