I have a whirlpool dishwasher model gu1500xtkq0, that is not draining out all the way. Once the cycle is over, there is still a good 2 inches of water left in the bottom. I first thought it was the check valve. Inspected it and it looked fine. So I'm thinking it is the drain pump that has gone out. I have found the pump on line for about $35. How involved is it to replace? Or could it be something else the matter with the washer?