Sexing mollies, swords, platties and guppies is really not that dificult. I believe that there is either a pinned topic on this or a very good thread in the Livebearers Forum. It's all about the anal fin shape - triangular in the female, straighter in the male. The male's fin has a name that escapes me right now, but he uses it to deliver the sperm "packets" to the female.
ALASKA