No worries, im new too, and i always forget to put it on my auctions :)
GIN means "get it now" - once you've been a seller for a little while you can set a get it now price, as well as a beginning bid. When a buyer chooses get it now, you get that set amount, minus the fees listia charges for GIN auctions. Hope that helps answer your question! :) xoxo
Oh, and be sure to verify at least two things (phone, twitter, Facebook, bank account). It shows bidders you are a serious seller, and a real person :) looking forward to bidding on your mommies girl. xoxo