It’s probably easier to just replace the switch, it’s an old switch anyway and mechanical parts do fail with age so even if you got it back together it might not last long.

I would just check the voltage for the country of purchase online but if you’re worried about the board, you can remove the 3 wires connecting to the board and test the AC voltage coming out of the transformer, the middle wire is your common and either of the sides should be about 18V. Unless there’s a part number written on the transformer to check which there wasn’t a lot of the time.

Assuming it doesn’t already have one, you should definitely consider wiring an earth connection to the pedal for safety’s sake.