Can the pump assembly for this unit be purchased separately?
Answer Hello Matt. The pump housing assembly is part# [WD19X10020].
Is WD26X10051 the likely culprit for tar-like grease spots all over the dishes and inner walls?
There is nothing in this unit that would cause a tar like grease to appear on the inner walls and dishes. It is possible that there is grease that was put into the unit that is getting spread throughout the unit from a dish that was put in the unit or over time from dishes in the unit. You will want to use a dishwasher cleaner to correct this issue.