2001 Dodge diesel, 3/4 ton, 4WD, ~35,000 miles

I'm not sure where exactly where the problem lies. Nobus is usually a bad ground or a loose connection.
You can try reseating all of the connections on all of the components that are on the "bus". The radio, the insturment panel, air bag controllers, etc.
Check all of your fuses first, make sure that one isn't blown out.
The EASIEST way to narrow down the culprit is to take it to a dealer or service center that has the ability to read vehicle specific codes. They will compair the list of components that the truck's computer is detecting, comparied to what's actually there. This problem sometimes, but very rarely, means that the ECM is dead. It is usually something less of an issue. Good thing tho, if it is the ECM it has a 8year 80k mile warranty as it is an intrigal part of the emissions system. Just make sure it's all free of mud, I don't know if water damage would be covered under warranty.