Sicce pump in a SWC skimmer

I had a LFS owner say that we could put a Sicce pump into my old SWC BMK 150 skimmer after the pump died. He mentioned something about getting it to fit and getting a new rubber gasket. Does anyone know how to do this and what I would need?

I don't even know where to find a gasket, I'm more of an electrical guy, and my mechanical skills only extend to woodworking. So I don't really have any experience with this type of thing. A link to directions, a picture, or even just the gasket that I would need would be great. I don't want to buy this pump then break the skimmer body or screw up the install.

Help please.