I did some training in regulator inspection & service, back in the days before the inspect replace rules came in. We were told never to try to repair the internals of a reg, that was strictly only for the manufacturers service department. All we could do is replace a damaged stem, nut or pressure gauge.
BUT if the safety flap in the gauge blew out, like in this case, that meant a drastic internal failure had occurred in the reg and that rendered it junk as the repair cost would be more than a new unit.
Like you I would have a go at repairing most things but if the regulator has failed the way you suggest UNDER NO CIRCUMSTANCES try to repair it - the consequences if you get it wrong are not worth thinking about.
I would suggest you go onto youtube & watch a few videos of what happens when the valves break off gas cylinders or the regs fail. That might change your mind!
BUT if the safety flap in the gauge blew out, like in this case, that meant a drastic internal failure had occurred in the reg and that rendered it junk as the repair cost would be more than a new unit.
Like you I would have a go at repairing most things but if the regulator has failed the way you suggest UNDER NO CIRCUMSTANCES try to repair it - the consequences if you get it wrong are not worth thinking about.
I would suggest you go onto youtube & watch a few videos of what happens when the valves break off gas cylinders or the regs fail. That might change your mind!