Sounds Like B.S. to me. Thats like saying the guy cant tie his shoe because the lace is in the wrong hole and it will take him 2 months to put it in the right hole. Maybe the guy is smokeing crack.
If the guy just blueing your gun. All he has to do is take it apart and blue the parts. It isnt rocket science and mausers are simple to take apart and reassemble. Pretty hard to mess up.