Here's a simple pulsein example for reading what the receiver is sending the servo's:

http://www.picbasic.co.uk/forum/showthread.php?t=12039


And I used the RCAP pibasic pro based autopilot on an rc plane. I know a few people that have used it to control RC cars. This requires a GOTO gps (like handheld garmin, etc). But for extra credit, the cordic could be used to determine the distance and direction from one waypoint to another ... that is, if gps was in your plan.

Some info, and the picbasic code can be found here:

http://en.wikibooks.org/wiki/RC_Airplane/RCAP

Walter