Eric is a very good source of Bravada info, most of it first hand knowledge.
Everybody has some tricks for heading off potential trouble on a used car purchase. Everybody does oil changes, my #1 thing to do is a transmission fluid & filter change to keep the good shifts.
Fluid checks to the differentials (as you well know) and transfer case should be done while the transmission fluid is draining.
Factory Service Manuals are frequently found on eBay at very reasonable prices....they are priceless for keeping up your Bravada.