A piece of cake. Follow the directions and take your time, and someone with beginners mechanical skills should have no trouble with this project.

Prior to reassembly, clean everything very well with clean paper towels, paying particular attention to removing the old silicon sealant (mine came off rather easily). Keep your hands clean when dealing with the seal, as any grit or dirt will ruin your best efforts (the pump will leak). I let my pump's silicon sealant cure for ~12 hours prior to priming the pump.

A word of caution, though - Even though I didn't touch the electrical wiring side of the motor, I turned off the breaker. You can never be too cautious.