Using the Jessica and Elexis models to replace Alyx.

I was looking to use the search engine for this but since the search function is down and after spending two days looking around Ask, Google and Facepunch, I decided to make a model request. I was looking to replace Alyx with either of those SINS Episodes girls ( ). If nothing else, could I at least be pointed in the direction of a tutorial for replacing Alyx with a different model? My thanks in advance folks.