Snaps basically are two parts that are peened together with a hammer and punch. It works both ways for male and female end, just different parts.
The female side of the snap is comprised of the backer, which has a flat base and a hollow post, and the female button.
To remove it, look inside the female button, and see if you can see where the backer post was peened down and mushroomed over to hold the snap in place. That is what is holding the two parts together. You'll have to figure out a way to cut off the mushroomed part to separate the two (dremel tool?). Unfortunately at that point the backer is toast and will no longer work, so you'll need to find a replacement.
Tandy Leather carries snaps, hopefully the same size.
To put it back on, cut the hole in the leather where you want it and push the backer post thru the hole. Then place the female button on the post, and then using a punch peen it down until it is tight. Tandy Leather should have the punch, and whatever else you might need. Hell, they might even show you how to do this.
Hopefully this makes sense.
