Except that a bass guitar is not life support equipment.
It is if you make your living playing bass. hehe
Actually, regulators are not life support either, this is a lie propagated by the dive gear industry to sell more expensive regulators and restrict service materials. If your life really did depend on your regulator working, there would be many, many more dead divers and probably very, very few people would choose to dive. I certainly wouldn't. This is why things like air sharing, alternate air sources, even CESA are taught. Air is life support underwater, not your regulator. Any decent diver knows to always dive in such a way as to have access to air from at least two sources, the second source typically being a buddy or the surface in recreational diving. Regulators are pretty reliable, but they do fail from time to time.
But even if it were true that regulator failure meant death, I would work on my own. These are pretty simple devices and what constitutes good service is mostly being careful and methodical, with a good understanding of how regulators work. Unfortunately you can't teach someone that stuff in a one day seminar that nobody ever fails, which the qualification for becoming a certified regulator tech at a dive shop. Some of these techs are excellent, some are not. How do you know who to trust?
Since your life depends on it, I mean. Come on, if servicing these things really truly had life and death consequences, don't you think the training would be just a tiny bit more rigorous?