My Duet stopped draining the other day. I checked the drain hose and everything seemed fine so I figured something was wrong with the pump. Not having any kind of instructions I lugged the thing (all 300 pounds) out of the drain pain and into the middle of the room so I could get the back panel off. As luck would have it the pump is in the front and can be accessed by removing the lower front panel. I tried that first, but it seemed to have hidden screws above (which it doesn't). You just remove the three screws by the floor and work it free (apply extra elbow grease here).
The pump has a simple plastic cap to expose the pre-impeller chamber. It turned out there was a small kids' sock in there. I have no idea how it got there because there is no hole bigger than 1/16 inch anywhere in the tub.
I am just writing this because somebody will eventually do a usenet search for this kind of problem and I couldn't find any such information when I looked.