$300 is about half the cost of a new rifle. As far as gunsmithing on the bolt, just for kicks I checked out a Tikka T3 Lite, chambered in 308 Win. I talked to a couple of friends with similar rifles (t3 lites) and we got together with the rifles, a set of Go - No Go gauges and 4 different colors of tape to wrap around the bolt handles and barrels so there wouldn't be any mixup when we went home.
Two of the rifles were stainless and two were stainless, even better for a cross check.
We switched out all of the bolts into every other rifle. All were in spec as far as the gauges were concerned.
These are mass produced rifles, not one of a kind knock offs. There isn't any reason to suspect that a new bolt, made on CNC equipment wouldn't be in spec or operate just as flawlessly or smoothly as the original. I can't imagine the Tikka factories individually fitting each barrel by hand on a lathe, it just doesn't make good economic sense.
If the rifle was accurate before, there is very little reason to believe it will be any different with a new bolt.
Now, the locking lugs may need to be lapped for contact (doubtfully) but most of us here would do that with any rifle, even just to check out a custom job.
Buy the new bolt, if you can get it into the country for $300. Then spend another $50 for some go - no gauges. You local gunsmith/shop would probably do it for nothing, if you bought a couple of boxes of cartridges from him or, more than likely just the good will. After all it only takes a couple of minutes.
You can do a rough check yourself by inserting a cartridge into the chamber and closeing the bolt, useing common sense and care, it should close and lock up easily. Next, take 2 pieces of clear, plastic, 13mm adhesive tape (appx .009 in) and stick them onto the back of the cartridge, trimming it to the edges. Then insert it into the chamber and close the bolt, if possible. It shouldn't close easily or at all. It probably will if you force it, as the plastic will deform under pressure. As mentioned above, this is a crude but effective method of checking headspace. bearhunter