First indication of a problem was water not draining at completion of cycle so I took the drain hose and check valve apart and sure enough found a cherry pit in the valve body.

I removed the pit and put everything back together then started a wash cycle but now theres no water coming in. The washer hums like it's going to begin a cycle but no water ever gets pumped into the tub. I'm wondering if it's possible another pit or something else may be jamming the pump. Looking inside the tub at the filter assembly I can see a white plastic ball loose on the inside of the filter assembly base which looks like the check ball (part 5 in the diagram) and some other gunk. I've tried to remove the 1/4 inch screw that I guess goes into the top of the impeller to get to the filter assembly but it's pretty tight and I'm a little afraid it'll break off or strip something if I torque it too hard. The dishwasher is only 2-3 years old so I would hope it can be removed without causing damage. Does anyone know if it's a normal right hand thread (turn cc to remove).

Any help would be appreciated.