1985 Dodge Ramcharger non working 4WD

I'm looking at buying a 1985 W100/150, but the owner says the 4WD doesn't work. He said his friend told him it was front bearings/hubs/etc. And parts would cost about $350. I've worked on plenty of cars, but never a 4WD, and wanted to see if this sounds right, or if I should be thinking transfer case. What questions should I ask to try to narrow down the problem?