Dodgy stick

I was given a stick to repair by someone as it wasn't detecting 'left'. I unscrewed the whole thing and when the metal plate that holds the microswitches in place was taken off, it works perfectly. Any suggestions as to what to do? I may still have a spare microswitch from years ago, but do you think it would be worth replacing? If it doesn'y work, what should I do? However, I do have a spare set of insides from an old battered stick that still work fine - I was going tomake a custom stick from that lot. If I replace it with that, how much should I charge him for the replacment?