This is exactly why I started servicing my own regulators while still a new diver. It is by far the best diving related decision I have ever made.
I think your last statement contradicts your premise, that new divers are better off with so called "professional" service. Certainly new divers are better off with competent and reliable service on their regulators, but the fact that many regulators fail immediately after service just underscores how incompetent many 'professional' regulator technicians are. The training involved is a one day no-fail seminar, with entrance requirements being that the tech works for a shop. This means any knucklehead from the sales floor can decide he wants to be a reg tech, and after ONE DAY, no matter how badly he does, he will be certified to do so. It's appalling how inconsistent and unreliable the standards are.