Welcome to the forum, Hopefully we can help clear your head!
Even though you are in AZ I woud start by getting the unit weathertight. Get those windows replaced. There is a good savlage yard in MO. called Colaws. They may have the windows you need. If yu are going to tow it for more than a few miles I would get the bearings and tires gone over before hand. Blowouts can cause lots of damage. Bearing failure will lead to axle replacement.
Since you are guessing at the year, you need to get it straight before you order parts. There should be a small 2X2 plate on the lower front right side attached to the skin of the trailer. Right side if you are standing in front of the trailer. We call that Road side. The side with the door is curbside. If you think of it going down the road in tow it makes sense. That plate will have weight ratings as well as the year and mont of manufacture. If you cannot find that there is a series of numbers on the plate to the right of the enterance door. Post the numbers as they appear and someone here can help to decode it.
As I said above, getting the unit weathertight is the first step. Once that is assured then you can worry about the interior and appliances. If the floor is in need of repair that would be the second thing to tackle.
Also as you look at this project you will want to inspect the axles and see if they are in need of replacing. Leaving a unit sit is not good for the axles. They like to be used, so check them as well. www.inlandrv.com
has a section on how to check your axle.
Good luck, and don't worry about being overwhelmed, we all get that way at times. It will pass, really, it will............