What do you mean by "refurbish"? What does it need? A good cleaning? If you're concerned about the propane/electrical/plumbing systems, call an RV supply/dealer and see if they do repairs and checks, if they don't they'll be able to tell you who can. Nearly everything else you can do yourself with hand tools and the knowledge of members on this forum.
Have you ever camped? As long as it's safe to go down the road and has no leaks
when it rains, you can consider it a hard-sided tent until you have it absolutely perfect for you.
BTW: you're very lucky to have grandparents to give you a molded lightweight fiberglass trailer!
Ask one question per topic and you'd be surprised the amount of help you will receive.