I agree about the Sprinter conversion book. It is a collection of threads, but it is a place to start out. If you can get insurance sorted out (so if the van is totaled, you get more than just the base chassis), and you read the bodybuilder's guide from Ford (not the one you get in the gym, but the upfitter's guide), you should have a starting point.
Again, read the Ford bodybuilder's/upfitter's guide. There are a lot of drill/no-drill spots, and it is crucial to make sure to mind those. Cut a CANBus wire, and you will be in a world of hurt.