Consider pressure testing the rig -- doesn't cost much and should expose actual or potential leak issues - big issue in used rigs.
In general your rig is broken down into two basic items Truck/Bus and RV stuff. Most RV outfits are capable of inspecting the RV stuff (fridge, converter/inverter/slides etc) - since your new you might consider calling around and asking how much they charge for an inspection. The Truck/Bus side of things is another matter - I personally would not trust RV guy and would prefer legitimate mechanic.
