There's been a fair bit of discussion on the M100 site regarding removal and replacement of the above pumps.
Some contributors maintain that it is necessary to remove the crankshaft pulley in order to remove the pump. Others advocate the removal of both pump and the housing it is attached to as one unit. I have found, without fail and each and every time, the pump can be removed without having to touch the other two components. Sure, it is a VERY close and tight fit as the impeller flange...