Normally the cap (capacitor) is placed in parallel with the motor, so if you can find the fly leads to the motor (the leads that come out of the motor) disconnect the cap there and put a new one in its place! Normally, motors are pretty standard eg shaft diameter, mounting holes or face plate mounting so you may well be able to get a different make of motor with the same spec and mounting method as the old one! As for de-energising the cap, the cap on your motor is very small and not worth worring about stored charge! If you are at all unsure about any of this, play it safe and get a sparkie to check it out, we don't want you getting hurt! It's easy on the net to give advice about electrics but without knowing your abilities, or if you truely understand what I'm getting at, it better to get a pro in!