It won't save you any money, and you won't do it enough to do a good job at it. (Kind of like fixing your car, but you can save money fixing your car because the car hand tools are not really specific). And you can destroy some expensive (and impossible to buy) parts when you do it, leaving you with no choice but to take it to a dive shop to pay the service and parts cost, plus the extra cost of replacing the part you destroyed.
For servicing my rental fleet, I have already spent $400.00 in scuba specific tools, and I still have some more to go. In my particular case, I can save money on repair bills because I am keeping 20 sets in order, and 20 kits times $50.00 annual overhaul fee is a thousand dollars.
All that said, both Zeagle and Dive Rite sell their parts kits to the general public. Those Dealers probably love to sell parts because it actually increases their repair business.
There are a number of people who repair their own gear on the these boards, and (hopefully) see it as an enjoyable activity, rather than a way to save money. Or as a way to keep classic gear (which has no manufacturer support) going. And there are a number of people who service gear for dive shops, who have gone to the manufacturer specific repair classes. (I am one. Off the top of my head: Oceanic, ScubaPro, Mares, Dacor, Sherwood, Atomic, US Divers, Apeks. The classes are not very in depth, but they provide a layer of liability protection.) Mostly, shop gear techs get their knowledge from doing repairs with the expensive tools that really only a dive shop can justify buying from an economic standpoint.
It's a simple thing. "Life support equipment" and all that verbiage aside. Do you feel comfortable free ascending, because of a gear failure, from whatever depth you dive to, and doing whatever surface swim that leaves you with? If the answer is yes, then go ahead and service your own gear. Because you are not going to be able to do a good job at it, if all you ever do is work on your own gear. You just will not get enough practice at it. If gear failures will inconvenience/trouble you, have someone with experience do it. Right now, I would say that the best places are the big online places because they do such a huge volume of repairs. But maybe they don't gear problems specific to your local area.
For instance, living in the Pacific exposes gear to much much much worse corrosion/rust/galvanic action than other places, and it also has bizarre problems like cockroaches eating second stage diaphragm, mouthpiece rubber, and first stage diaphragms. If you live on Oahu (Honolulu) in Hawaiii, you have a guy (one of the few I have ever heard of) who is not shop affiliated, who is certified and experienced in every regulator you ever heard of, and many you have not, plus has the local knowledge to deal with Hawaii specific problems. He's so good that many shops just send their repairs to him, even though it's a two week turnaround usually. And those are people working at dive shops who have the full setup (tools equipment and parts) to do repairs. He will just do it better. It's all he does, all day long, is repair gear. (And teach tech classes for the manufacturers, because he knows more about the gear than the manufacturer's reps.) And then he goes diving at night.
