Well, you've come to the right place!,
Welcome to the forum and the best place to start is to just do a search on the particular item you are looking to fix.
I would start by assessing the exterior and structural condition, sealing any leaks, checking the axles, and looking for rear end sag or separation. Get the critical stuff out of the way and you will feel better about the petty things, like dropping $700 on new curtains or $1400 on a new fridge.
Figuring out what your end usage will be most helpful, if you are going to drag it around the country then new tires, brakes and possibly axles may be needed, if you're gonna park it and live in it then maybe not and so on, , , , ,