Have them demonstrate that EVERYTHING functions. Make them move it, run it, or whatever it does, be sure it works. Tell them to have the frig cooled down to temperature, not just show you it is getting cool.
Have them watch/help you do everything required to hitch/unhitch and completely set the camper up for camping, including leveling, etc. I don't care if it is winterized, have them put water in it and check everywhere for leaks and make sure the pump doesn't cycle due to leaks. They can re-winterize it after the PDI, don't settle for anything less.
Don't be in a rush to hook up and head home. Take an hour or so just to be in the unit and look around. You are liable to notice things that need adjusted, touched up, etc. Easier to get it done before you leave.
Ask them to check the lug nut torque with a torque wrench and also check the spring hanger bolts and U bolts.
It is your money, don't be rushed.
2016 Duramax - 2010 CF30SKP
Viet Nam Vet 70-71 Da Nang
Real airplanes have two wings and big, round, engines