It looks like you double-posted this thread. Anyway, here's a class.
Regulator Service Technician Training - Unrestricted
I personally learned watching a few videos on the subject for the MK5/MK10 first stage, and the G250 second stage.
I haven't taken apart those specific regulators yet, but in my experience 2nd stages are pretty easy, and require no special tools. Usually, it's just items like an o-ring pick and wrench is good enough. Scuba-pro likes to use an unusual nut, but I just wrap it in cloth (to prevent scratching) and use a wrench. I'd say learning to remove the cover, diaphram, and rinsing it out is a really easy good start.
1st-stages tend to require more specialized tools, or at least a couple correctly sized spanner wrenches.
Scubapro Multi-Tool, Aluminum You'll also need a piston-bullet and an assembly-tool for the inner-o-ring like this:
Scubapro Mk20/Mk25 Assembly Tool.
Compact IP Gauge (PSI and BAR) You'll also want an IP gauge/ I'd say second-stages are twice the level of complication as 1st, probably wont save you money (versus paying to have it serviced), but are very doable. The up-side though is mostly that I can service or re-assemble it at any time. If you want to do it right, some torque-wrenches are also recommended.
Home | Vintage Double Hose Has a lot of manuals. Scroll down, manuals and catalogs, then Scubapro.
Lastly, make sure service-part-kits are available. Scubapro likes to make it more difficult to acquire part-kits. Anyway, there are a bunch of people hwere who know far more about servicing than I do and will likely chime in shortly.