The fridge is basically just a heating element; it's probably burned out. That should be an easy repair. I would absolutely make the renter pay for all the damage. You can't "accidentally" plug it into 240v. The 30A RV plug is a 120v design. The only way you can get 240v on it is to mangle the blades and jam it into the wrong rec or build your own crazy adapter. What I'm saying is it was intentionally plugged into 240v. Not that he was trying to fry it but you have to really try to do what he did.
I'm assuming, of course, that this is a 30A RV. If you have a 50 amp service that changes everything. Those are 240/120v.