I've always gone to Burning Man (and anywhere else) in my own trucks, always older ones.
There's a lot of money to be saved and a lot of convenience in having your own truck vs. renting them, but you have work to do if you don't want trouble. $1000 - $2000 will get you a solid truck, but reality is you need to spend a bit more on a few key items if you want to be reasonably sure of making the trip.
First, you can test-drive around town all you want, but you don't really know what your truck is made of until you load it heavy and point it up a mountain pass. The two biggest heavy-load, steep mountain failures are overheating and transmissions.
Get a new radiator, whether you think yours is fine or not.
A stick trans is highly preferable for this kind of duty, but they're rare in vans or box trucks. If you have an automatic, get it rebuilt whether it seems fine or not. The older, non-overdrive ones like the older trucks we're talking about will have aren't nearly as expensive to re-do as the newer ones. It's basically impossible to accurately asses the condition of an old auto trans. I'd never head over the mountains to BM in a loaded truck with an old unknown-shape automatic.
Don't just leave it in "Drive" and floor it up the hills! That's when you'll blow it up! You'll heat the hell out of the transmission and motor. Slow down, shift down, let up on the gas, and walk it up the hills easy. Be nice to the goddamm thing.
Look at the tires. Tread depth isn't that important unless they're bald, what's important is the sidewalls. If they have cracks, they're trouble waiting to screw you somewhere. Inflate them to the max. pressure indicated on the sidewall fine print.
Replace the belts and hoses. Little shit like that will ruin your day.
GreyCoyote: "At this rate it wont be long before he is Admiral Fukkit."
Delle: Singularly we may be dysfunctional misfits, but together we're magic.