Re: parts
Hours doesn't mean anything on the bellows, and for that matter engine either. Except for oil changes.
If it's the original bellows, or you have no idea how old it is, yes replace it. As far as the cable, if it works free and doesn't bind or have rough spots, it's fine. If the switchs work, why replace them?
Even if both switchs went bad, you could still run the boat and fix it when you want to. (if ever)