Woah that's pretty cool! A true California car, it has the floor temp thing for if the cat gets too hot.
It will definitely be a bit of work, but it'll be worth it! That glass looks like it's in really good shape, which is nice! From the pics your rust looks pretty minimal as well, another plus! The floorboards in specific are nice for its age.
That yellow thing is the coolant overflow bottle, so you might check your coolant level. It might be overflowing onto the ground over time, and causing the overheating problem.