Update so far:
I printed everything I could find on this subject and took it into the dealership. They thanked me for it! They DID find a faulty connection on the instument cluster, and fixed it this past Monday. Wonderful! At least it would be if the story ended there. However, on our way back home, a 6 hour drive, everything started to go crazy. First the tape player started to go on and off (we were listening to it at the time) so I shut if off, but then the clock flickered and went out. Shortly after, all of the gauges on the dash started to independently jump all over the place, the windshield wipers started to go, and even the door locks went up and down! I also lost some power and had to drive slower as the engine was revving quite high. Eventually the gauges slowed down and stopped entirely, but we kept limping along to try to reach the next city just a few miles away. Just before we got there, everything suddenly came back to life! For various reasons we decided to keep going, and drove another hour and a half, but when we stopped for our son's bathroom break, the van died when we tried to leave. Unfortunately, we were still an hour from home. The service engine soon light and the voltmeter light were both on, and apparently there is now something wrong with the charging system. We let it sit and after awhile it started, but just could not keep it running. So, it is now back in the shop, one that is closer to our home, but one that hasn't been working with us to solve this. (The other dealership was one that my parents have been dealing with since they originally bought the van, and we are now buying the van from them.) If anyone has any further suggestions, that would be great. They haven't started to look at it just yet so I don't know what any of the codes will be.