Dishwasher wouldn't drain; pump drain impeller had come off drive shaft.

Replaced the pump drain as one complete assembly. Couldn't do it from under the front panel as there is a small lug that you have to depress on the top of the assembly before you can twist the assembly counter-clockwise by hand. I tried but I couln't get the leverage. Had to take dishwasher out from under the unit and tip it on its side. The rest was very straightforward. If you can remove the dishwasher from under the unit easily I would suggest you don't even bother trying to change the pump drain while the dishwasher is in place. It's not worth the hassle.