Feel freer to ressurect it as you need to. I don't see anything wrong with a rebuild motor as long as it was done properly. Get the paperwork to see it was done at a qualified shop and find out why it was rebuilt. Most common is blown headgasket. In that case they usually machine the head and put it back on. They don't usually do a full tear down and rebuild. But the paperwork is essential. Anyone who paid to have it done is stupid if they didn't keep it. Either that or their hiding something.
By almost restored do you mean out of your price range? I don't see anything wrong with body Rudy because that's cosmetic. Which is easily fixable. You can take a course in body work and fix it yourself. You need to be concerned about structural rust. Get under the car and look at the frame. If their are holes in te frame from rust that's bad. Rust on structural areas bad. As long as the frame and drivetrain are in good shape the body shouldnt matter to much. Same goes for interior. Seats ripped to crap? Sweet, throw in Recaro's! That's how I see it.
These motors have been known to hit 1 million miles if properly cared for. And if Someone has properly cared for it they should have te paperwork. Just look at all the cars in your area. Each one you look at will give you an idea of what is out their first hand, what shape their in and what to look for each time. Don't let a seller try to scan you. If it seems fishy walk away. Take your time and look at everything. BMW made 350,000 E30's per year so their will be more.
The E36 used plastic company's in high stress areas and in non stress areas. When theirs heat it causes the plastic to become brittle. Web working on te car with the plastic pieces you just have to be careful not to break it. The only issue was the coolant system but of that's been replaced you should have no issues. I drove my E36 for 3 years after we did te coolant system and it hasnt overheated since. Reliability has been excellent except for three issues which are common, and fixable without killing my wallet.