The recent question about removing the stereo reminded me of this site:
    http://www.the12volt.com/
You have to register to get to the best stuff, there are ads, but everything loads
fast.
There is a MASSIVE (sorry for  the caps :)) amount of information about everything
relating to vehicle audio, alarms and cruise control, and yes, there is information
relating to Vanagons (RVC). From the most basic electronic concepts to the most
technical. And if you can't find what you need, there are forums where you can ask.
Check it out.
Jerry