First of all, congrats on the new to you pup and welcome to the forum!
Mine had an inline fuse near the battery that I had to replace to get anything to work off the battery.
Be a little patient when trying the furnace. It may take a few attempts before air in the gas lines gets cleared out. Also when you get around to trying the frig it can take a few hours to a full day before it gets cold.
It might be worth the $$ to take the pup to a nearby dealer, have them go through it and then have them do a Pre Delivery Inspection (PDI) with you.
Good luck and happy camping!
Thank you! I will have to do a little research to find one near to me.