Very nice looking trailer! On this one, a restoration doesn't look to be all that much. You should definitely look at the tires
since they can look great on the outside but be pretty shot inside. Years of sitting outside matter more than mileage. Most people have removed their swamp coolers since they tend not to work well anymore and, if they do work, just make the air more humid. A new vent fan (Fantastic Fan, MaXXAir, etc.) can be purchased to fit that ceiling hole well. The CTs weren't really made to support a modern roof AC, so the fan is the best way to go. For the broken door lock/handle, you can have the lock repaired by a locksmith if it is not too far gone. The broken handle may be the bigger problem though, since I don't know if that part is replaceable. The lock mechanism appears to be the same lock as found on all the UHaul
campers (Bargman but I don't know the number), so these can sometimes be found on eBay or in the used parts section of this website. (Be sure to wash out that fresh water tank, too, to take care of any growths or bacteria and check out the battery
Window seals are a problem on all of these older UHauls, so expect a little dribbling water. There are lots of posts on this forum about putting in new seals or at least temporarily stopping the infiltration. I used black butyl putty to solve our leaking problems on the back window.
The broken therostate prong is something I haven't had to fix, but again, there are posts about fixing/replacing thermostats on this forum. Some folks just go with a newer furnace
or look for a used thermostat for sale
Overall, this looks like a good buy in the new price range. Cute trailer!