[MINICooperS]

Okay, I've found the leak on my dishwasher pump and now I need to remove same. Have located the large plastic nut inside that holds pump to washer. How is the lower spray tower/arm attached so that I can remove it to get the pump nut removed? Also, since I imagine this nut is going to have 10 years of soap scum on the threads, is there a preferred method to remove the nut? Special lubricant? Special wrench?
Thanks

[MINICooperS]

I need to know how the motor shaft is held into the impeller so I don't break something trying to remove it. The shaft is rusted from the seal leaking but I'd like to explore all options before replacing complete motor/pump assembly which would be about 50% of just buying a new dishwasher.