What to do with project '79

I have a 1979 mustang I recently picked up. Sat in a field for 21 years. It currently runs and drives. Surprisingly, the only things that don't work are the radio and dome light. It truly did not put up a fight. Its biggest problem is the paint. It is terrible. My question is what is the point of diminishing returns for these cars? I would like to paint it myself but that would likely be a $1000 project. Needs a lot of prep and has a handful of rust spots. There is, however, a brand new interior still in boxes sitting in the back seat. Would it be worth painting it?

5.0, C4, 4.10 Limited slip.