Yesterday the dishwasher stopped getting dishes clean. The same dishes went through 3 cycles and still nothing on top rack looked like it had been touched, bottom rack just a little better, but soap was on dishes closest to dispenser in large blobs. Strainers and wash arms are all clear. Sounds different when it runs; perhaps not pumping water. Goes through full cycle, fills, drains properly. When I open the door quickly in the middle of a cycle there is minimal activity down below, and no sign of water coming from upper arms. Is this the circulation pump? Could it be anything else, before I order a part? How does one go about replacing this part?