My in-ground pool pump hums when I turn the power switch on but it doesn't start. If I leave the power on for too long it trips the circuit breaker. The pool is 10 years old. Do pool pumps need to be oiled? I thought they were sealed and required no additional lubrication.

They need to be maintained like any other equiptment. If you don't know how then its time to call a professional in and have it looked at.

The bearings are locked up most likely, take the hair and lint basket out and turn the power off and seee if you can turn the impeller if you can then something else is wrong with the motor in either case over 10 years old replace it

You could take the bacend housing off with a 1/4 inch driver and remove the screw holding the start capacitor on and put a 7/16 wrench on it and work it free