As far as the barrel goes you could do a chamber cast with "Carrowsafe" from Brownels or have a gunsmith do it for you. IIRC the field test bolt is designed to be used with headspace gages "in the field" to determine if a barrel or receiver needs to be replaced.

I'm not very knowledgeable on 03's, perhaps someone who is will chime in.

$400.00 seems reasonable [to me] if your willing to take on the project.

HTH

Bill