Thanks everyone! Babystarz thanks for the eBay seller recommendation, nice to know someone that has bought from him and had no issues.
I have read a lot of posts that they will multiply quite a lot and possibly take over the tank. I've also read a lot of posts from people that say they don't have issues with overpopulation. Some say they will only overpopulate if there is an overabundance of food, others say in a matter of weeks they took over their tanks... so I guess it's a toss up but I'm willing to try it as the benefits seem to outweigh the risk. I've been "poking" the sand to aerate it, but I've recently added more plants and some don't like their roots disturbed. I also want an algae eater so a trumpet seems like it would address both those issues. Also since it's only a 6 gallon I don't want a snail wit a high Bio load.
I've read that if you do want to reduce the number in your tank you can set a glass jar in the tank with a piece of lettuce overnight and a lot of snails will converge on it, then you just take the jar out so that's a possibility if I do end up with more that I'd like.
Thanks again for all the help / suggestions.