Figure that you might NOT get it back, and make everyone who uses it chip in. Then keep the doors to the cab closed, don't aim the big door South/Southwest, and just do your best.
(Take it to a truck wash; Google one in the city you return your truck in. And sweep/swiffer out the back, clean DRY so as not to make a muddy playa scum on every surface; see the threads about cleaning and dust-proofing.) The Budget Truck Rental on Gentry Way in Reno is Burner-friendly--so lets keep 'em that way--and (I believe) has given Junglesmacks his deposit back after doing a decent job. But no one can tell you for sure.
If I were super-comfortable driving something large, I would easily go for a box truck and skip an RV (unless I owned one already, or a good friend did . . . because you can take your time cleaning it when it's yours). Then again . . . I'm really comfortable with a solar shower, evap pond, pee bottle and funnel. Out on the playa I'm not the delicate (noisy) flower I am in the default world.
Note: RVs do have the edge where it comes to beds. In a box truck, you will need a cot or air mattress, and layers of blankets. Air mattresses in particular conduct cold like nobody's business.