There's not really a good forum for Unimogs. A buddy of mine has one and the best info he got was from this low-tech mailing list-
http://www.tx4x4.com/. Pirate4x4.com has a Unimog forum- but it doesn't get much traffic. Try expedition imports too, they sell parts and service. They also have a big for sale section- good to get an idea of what various mogs are going for.