The switches linked by aholtzma look good; you probably want an on-off-on switch for your power swtich, and an on-on switch for your polarity switch.
I would guess that the glue and black rubbery stuff you're complaining about is a sealant that they use to make the subwoofer enclosure airtight to improve the sound quality and keep things from rattling when the sub is in use.
As for the original problem, the component that tends to fail most often is capacitors; do yours have any bulging or discoloration?