You know how to tell if an rv salesman is lying, right? If his lips move... ;)
I think Xterras might be rated to tow 5000/500 with Auto and wd hitch, or 3500/350 with stick. A dealer can run your vin and tell you exactly what YOUR truck can tow.
Suppose you have AT. Where is the fresh water tank on that unit? If up front, you'd have to travel without water. I would go back to the dealer and have them weigh the tongue (right under the ball socket) while a full LP tank and a battery are sitting in place; if that weight is under 450lbs, I'd say you might make it work with a lightweight WD hitch. Maybe! But you would have to load gear toward the back, and constantly worry about it. Not fun.
CL16BHB has the lightest hitch, 300 lbs.
A 16' Scamp would be a good choice.
What do you teach? I taught 7th grade math last year. Hoo wee! Back to the business world for me, I loved teaching but hated the disrespect and misbehavior and sheer laziness.