The key to an old trailer like that is the fridge,if it doesn't work the trailer is not worth anything if it works well then it has some value.If your a handy guy than fix what you can and don't worry about the rest.You have heat and a fridge thats way better then tenting.I had an old one just like that the brakes didn't work and i pulled it and stopped it no problem.Pending on your truck i suppose.Anyway my thoughts on this are you don't need to have it all working, if the water pump doesn't work big deal bring a water jug.The dealers are going to charge you threw the roof 100$/hr at least and parts will be very pricey.The only thing i would suggest is get the wheel bearings re-packed,brakes if you think there toast,any leaks just stick some silicone around it and your good to go.