I wouldn't worry about the barrel (assuming a halfway decent bore) or receiver. There's so much metal in those that they could probably be made of pewter and still be safe.
I'd want to replace the bolt first chance I got. I'd also replace the pin-dealie that stops the bolt.
If you paid $100 for the "project" to start with, you could well end up with more money in getting it shooting again than a decent used shooter would cost in the first place, depending on what a bolt (and other parts) would cost. So what's the point? Three things:
1. You can "pay as you go," you don't need to whip out all the cash at once.
2. You get a lot of fun and satisfaction out of bringing a project like this back from the dead.
3. You get a great story to tell and amaze your friends.
I love projects!