As to the bolt, if you're concerned, you can dye pen and or mag it. If you have the barrel off and there's no indication of setback on the lug abutments, the bolt is likely fine. What I would look for is gas cutting on the bolt face.
For screwing a factory tube on, I would see if it indexes and headspaces without work, if so....should save you money. If it needs to be spun a thread....I'd punt and call bugholes/redhawk/precision....etc and get a tube in the mail.
Your setup time is 60+% of your cost. If you have to pay that, might as well spin up a winner.