If you hate the dents in the sides now you aren't gonna like them any better later. As for the bumpers, it's more rare to have a 3rd gen without dented tin foil than with.
Did the 99 have 16's? Really no rust? Anywhere? Isn't it from IL? Don't be surprised if you find stuff underneath, salespeople don't get under the vehicles. Here's a couple of pics of 'rust free' trucks, the 96 and the 99. One spent half its life in CA and has been here for 7 years now, the other AZ, TX and a couple of years in WI then a couple of years here...
That first pic is actually my 96 with 233,000 miles. The nasty pic is the 99!
So anyway, watch that rust.
What's been replaced?
Ball joints?
Sway bar links?
Sway bar bushings?
Steering rack bushings?
Inner and outer tie rod ends?
Lower a-arm bushings?
Does it sag? Are the shocks shot?
Is the power steering rack leaking?
Any evidence of rear axle seals leaking?
What do the front seat mounts look like (cracking?)
Do the rear light/defrost/wiper work?
Does the antenna work?
Does the a/c work?
What do all the fluids look/smell like?
Pink milkshake??? Has an oil cooler been installed/rad replaced?
When was the t-belt replaced? At 90,000? At 180,000? ie; when next due?
What do the cv boots look like?
Has the engine been treated well? I've seen some nasty sludge under the valve covers threads from non-maintained 3.4s.
How are the seats?
Plugs? Wires? How's it run?
Are the rotors warped?
Well, that's a start at any rate. 'Course, the 6 grand difference in price could net you a really nice truck but you may have to do a bit of work to get rid of some bumps, clunks, and so on. Mine's got 233,000 and other than an engine tick I haven't gotten 'round to locating it feels solid to drive and it runs well. The above list is some of the maintenance I've done to it the past couple of years- other than the auto tranny stuff 'cause mine's manual. I did replace the clutch though.
It's actually been a fairly easy and fun truck to work on 'cept for the tranny/transfer case 'cause it's HEAVY and getting the crank bolt loose....217 ft lbs, oy...