I've got to rebuild the pump on our W-C Head-Mate. I'm definitely not looking forward to that job, after all I've read here.
I may be in luck, tho. The head was never used by the PO (or so he said), and we've used it only little since we obtained the boat. I believe the output from the head enters the tank high. So, God willin' and the creek don't rise: I may get away with just closing the intake thru-hull and pulling the pump assembly off for rebuild. There shouldn't be much mess.