I agree that the bodywork, engine, interior order makes more sense when you think about it, but practically the interior is going to be a lot cheaper to put right than the bodywork, and you can do it yourself. It's also something you can do bit by bit over a long period of time.
If your engine is at 150k, is clean, has no problems and still feels strong, I wouldn't bother messing with it unless you want to put something bigger in. I've often seen 150k quoted as the point that a valver needs a rebuild, but I have seen some on 200k+ on the original engine, and mine is at 170k with no problems.
It also my be worth getting it rolling roaded to see how much it is putting out at the moment - if it is close to, or exceeds the factory figures then it becomes a lot harder to justify an engine rebuild.