RV fridges take a good long time to cool down. Yours may well be okay; typically once they leak they lose all cooling ability pretty quickly. Give it a day's operation and see how cold it is. (For the price of a replacement RV fridge, you can buy a nice cooler and a lot of bags of ice, incidentally.)
Do a thorough inspection of the sealing/caulking around the roof. Water intrusion can cause major damage in a remarkably short time, and previous owners may not have been super vigilant on this since they kept in in a garage. Also check the date codes on the tires and have them inspected for dry rot, etc. if they're over five years old (and just replace them if they're too much older than that). RV tires, as you may already know, usually have to be replaced due to age before the tread is worn down.
Have fun and make lots of great memories! It's often a good idea to try your first camping trip in your own driveway or backyard. (A trip of several feet still counts as a trip, just a rather short one.)
