Welcome. I am far from an expert but I looked at the pictures you posted and will offer an opinion on what I saw of the rust. Fix it, doesn't have to be perfect but fix the major dents and at least sand/convert the rust and put some primer on it.

You will have plenty to do to get ready for school, the least of which is body work. Take the local guys up and get the cage inspected and make sure all of the safety stuff is done up front while you are getting the rest of the car operational.

THe Savannah school is probably the best value out there for a 2 days school. You will see 6+ hours of track time and the car will need to be rock solid mechanically.

Good luck and once again welcome, I still like old Datsuns for some strange reason......

Paul