Well, just use your head and get your hands dirty.
I just bought my '00 and I'm satisfied. The motor was CLEAN. Now, some places get 'crafty' and clean the bay up with products like WD-40 and make things look all nice and pretty, but certainly not clean.
Biggest things, PULL THE STICKS. Even the most novice of buyers should do this. Look for grit or odd smells, oil should be honey brown, trans pinkish-red. Dont' be afraid, 9 out of 10 times this alerts a salesman that he's dealing wth someone who isn't going to settle for a vehicle that been rigged to get off the lot (AS-IS) and die a block later.
The lot I got my truck from was trying to push this p.o.s. Dakota on me that when I started it it spewed a plume of gas out of what was left of the exhaust and when I tapped the throttle it hung up. Salesman says, "oh it probably needs to be lubed", heh, I pop the hood and there's the remnants of a mouse nest jammed between the intake and throttle body case, no sale buddy.
Certainly as with any SUV/Truck, a thurough exame of the trans is a good idea especially when there's a tow hitch, some folks like to disregard the weight capacity which equals death.
When you test drive, TEST everything, that's why it's a TEST drive. With any used vehicle, you have to make some compromise, with mine everything mechanical checked out with the exception of rear wiper, so to me, I think they are a silly idea in the first place, so since everything else works, I'm not losing sleep over it. Oh, and once you've comfirmed the radio works, shut it off and listen to the vehicle for odd noises, not the tunes.
As for belts and batteries, they may throw you a 'used' battery, but don't expect much. A belt, you'll probably be told to have a nice day.