We properly finish regulator service work for do-it-your-self'ers quite often.
It's easy to tell if somebody who knows what they are doing is doing the service work.
A properly trained repair tech won't scratch gouges in an O ring track and cause a non-repairable creep and ruin the regulator body, or leave tool marks in the brass, or overtighten everything to the point where you might destroy it during disasembly next year.
Most divers don't have ultrasonic cleaners, torque wrenches, brand specific tools, parts schematics and access to proper service parts.
GOOD service tech's attend a factory sponsored clinic every year to stay current on every brand they touch on the work bench.
What do you really save if a problem causes you to miss even one dive?