Remove the 3 screws on the front with 1/4 inch nut driver remove the diffuser and mounting plate remove cap covering the bolt head on the back of the motor hold the motor shaft with an ajustable wrench or vicegrips turn the impeller counter clockwise it should only be hand tight unscrew the impeller

How do I get the impeller off so I can replace the motor?

Pull harder is a good thought, but if you can still get the bolts back in easly with the band off and the pump full of water turn the pump on for a second. but if the motor won't run GENTLEY pry on the case where the clamp was, being careful not to hurt the caseing.