RE: BARREL CHANGE
Rather than buying a new bolt/bolthead, I'd ask the 'smith if he can install a bushing in the existing boltface along with a Sako style extractor. The bushing could be made to much greater precision than the existing boltface (more accuracy), it'd probably be cheaper than buying a new bolt and then having it trued up (you are having the action blueprinted and accurized while the barrel is off, right? if you don't, then why bother changing the barrel in the first place.) Plus you get the Sako-style extractor which is a nice custom feature in itself.
Mike