Database Driven Website

I am planning a website that will allow for the purchase of digital material to be downloaded directly after purchase. There will be multiple contributers of material to the site. I will need for visitors to be able to sort available products by several criteria, including designer, type of product, price range, etc., then to display individual information about products once selected. I will need a way for designers to upload their offerings, and to get a status account of their sales. For memebrs, I will also need a secure member area. Ideally, I would like someone who can teach me how to do this as it is being developed, so I can maintain it myself, and recreate the process on a second site if desired. No graphics work or page/layout design is necessary. Just the underlying data processing. The possibility of a long tern association exists for someone who might be willing to exchange their work for a percentage of profits. If you would like to see a site that represents my ideal check out www.pixelmill.net.