Have you checked with NADA to get a handle of their appraisal? It should give you a ballpark $$. Seeing as it's your first RV I would suggest taking along a seasoned RV owner, if you know, one to give it a good once over. Have the dealer hook it up to water and electric and check everything, run all the systems, put some water in the fresh water tank and check the water pump. Try the furnace, AC, all electric outlets. Does the fridge cool, stove work? Get on the roof and look for tears in the roof membrane check all the caulking while up there. Look and the front, back, and side walls and check for delamination. Look at the tires, ask if they know when the bearings and brakes were last checked. Run the awning out and look for tears/rips. I think by now you get the idea. You really need to check everything because once the paperwork is signed it's all on you.