They're pretty straight forward:
Light is produced by a xenon lamp which needs several hundred volts potential plus HT to strike the arc.
You've got 12V going in, this will be boosted to several hundred volts by the transformer and drive transistor, the white capacitor in the handle will store...
Plug or spot?
If spot then you really need to get back to a single flange thickness so you can clean up well enough.
If plug then it could work but not a nice solution, technically unless you plug at original spot position you're not restoring to original structure..
It doesn't take much to...
That's not a patch repair, the suggestion suggests customer wants it done on the cheap. If repair section available then not too bad a job providing you get to good metal eventually.
Wet the area then observe the reflection. When filling, the usual mistakes is to rub down too much....in your case you're going to need filler over and beyond the high spot....unless you intend to remove the high spots.
Sounds like you want the socket behind a wall mounted TV - in which case down from the top probably isn't as bad as you might think. Remove plasterboard at noggins and drill through. A lot will depend on what access is like from the top.
Old gravestones used to have lead poured in the characters, you'll often find them on the ground around the base as the stone crumbles - a few holes drilled at odd angles helps retain them.
Gold leaf would be an option.
I had a print going this afternoon in black resin so threw a few of these on the bed, scaled the original 15mm diam by 66% to get 10mm...
Print was fine except for one small area.