I like to think that I'm smarter than the average bear when it comes to technical things like this. I was formerly an automotive and aviation mechanic. I actually really like the idea of tinkering with my own gear, so I may keep my eye on the used market anyway. I also have a passion for reviving and using old gear. I still have a Windows XP PC from 2002 that honestly runs better than most of what you'd get from best buy. I realize that's a lot different than a regulator at 60 feet.
This also wouldn't be the first time I've taken my life into my hands, I participate in quite a few extreme sports and have always trusted my own work over that of another shop or tech. Diving is a new experience for me though as the risk is much higher.
Here's the deal with servicing scuba gear. Regulators (and a few related bits of hardware including tank valves, hose ends, and inflators), were made to be serviced and rebuilt. All the wear parts, mostly o-rings, are replaced during a service. The manufacturers have service kits for their regulator stages that include all the needed replacement parts.
The big issue with DIY is that the mainline manufacturers do their best to block self service. They do not make service manuals available to the public, they won't sell parts or service kits directly to the public, and they won't let their dealers sell them either.
It's possible to work around all of this. I happen to like Mares regs and so I've built up a
library of their manuals. Forum member
@Tanks A Lot has an extensive collection of manuals and other info as well. You do need to
sign up to access it.
I've ordered parts from Italy and from a shop that had dropped their dealership agreement with Mares and so was free to sell of their remaining stock. Parts and service kits also appear on eBay regularly. Finally, since the service kits are generally made up of off the shelf parts, there are aftermarket companies like
scubagaskets (service kits main page) that assemble kits for you or you can source your own stuff.
Another option is to get regs from one of the few sources that support DIY repair. Deep6gear.com is the best example. They make their excellent service manual (written by forum member
@rsingler - an anesthesiologist who moonlights as a reg tech instructor and troubleshooter for his local dive shops) available to all. They sell service kits to anyone and other parts to anyone who has taken their class or can demonstrate that they won't hurt themselves. I'm not sure if they'll accept an A&P certificate, but they do accept certification on other reg types or rsingler's class.
www.deep6gear.com
Other DIY-friendly options are HOG Edge which allows you to buy parts if you take one of their service courses offered through TDI and the aforementioned scubagaskets which has just started marketing their own regulator.
Outside of regs, scuba gear is not particularly amenable to self-servicing. You can replace fin and mask straps and probably swap the battery on your computer. You can patch holes in wetsuits, but neoprene is inevitably going to degrade over time. Traditional BCDs are made of laminated fabrics and are designed to be disposable. That's one of the many reasons why a lot of us have switched to backplates and wings.