the rebuilt and new master cylinders that arent AC delco are all crap - thats a known fact on here. would you want your kids/grandkids riding around in a car that has half working brakes?
ANY repair shop would honor the part replacement but they arent going to get you a freebee on labor.
while the last line you state about any car is a reflection on how well it was taken care of i fully agree, but when was the last time you saw a chevette for sale for less than $800 that didnt need just about everything to be a safe reliable daily driver or have severe rust issues?