Creating sign-up page and store template

Does anyone know of a tutorial or something that can help me with setting up a multisite marketplace site? I have a site(multisite install) with a store (marketpress) that I created. The part I am stuck on now is that I want to somehow create a signup page so that people can click on a signup button and answer some questions and create their own store to sell products on my network. I want there first page to just be the store that shows products and allows them to add products as well as a contact me page and I am just a little confused about where to go from here. My site if you wanna look at it is It is my very first website and I am very new to this so try to go easy on me lol