Use some egg crate and filter floss to cover the pumps intake from your sump to prevent stuff from being sucked in, like making a screen for it. You will have to keep an eye on it and clean the filter floss occassionally, but it will protect your pump.

As far as cleaning the Iwaki pump, there are screws (6?) that hold the impeller housing to the pump body. You can remove the screws and take the housing apart to clean it and the impeller. When you put it back together again, just be careful that the rubber seal/gasket sits in the groove correctly before tightening the screws all the way down. If you pinch it, it could leak.