Be sure to discus this with the dealer prior to the PDI/Delivery walk through. Don't just assume
they'll do it. Basically, I'd expect them to do everything they'd do for their pricey "end of season maintenance package" at no cost to you.
That would include a thorough cleaning inside & out (including the roof), an exterior waxing, an inspection/maintenance of the roof seams, A/C, vent, and window seals, test of the propane lines, and a test of the refrigerator coolant. In addition, they should repack the wheel bearings. After 2-3 years of setting on the dealer's lot (depending on the actual build/ship date), the grease will have deteriorated and gotten dirt/moisture in it. Check the tire sidewalls before they put on the "tire shine". If the sun is intense in your area, there may be some checking or cracking. If so, they should replace them. (They should be fully covered by the tire mfrs. warranty.) All of that is in addition to their normal PDI procedures.
My TT sat on the dealer's lot for a year and three months before I bought it. That's what I had them do before I'd accept it!
Congratulations, and happy camping!