Build an Online Store digital downloads vendors login page etc...

need a store created for digital downloads (gaming add-ons) need a vendors access area so they can check sales, but I will be the one building each product page, vendors will not have access to that part. will be doing some limited sales where drop-shipping will be required. we have about 300 vendors each with 10-150 products each. I want to design the basic graphics for each page, fonts, logo etc... the layout of the store will be almost exactly like this store, [login to view URL] - but with different fonts, logo, etc.... I need the store to be available to be translated into various different languages. users will receive a confirmation email and a link to their downloads. also need to have a users login so they can access any of their downloads at anytime. some vendors have serial numbers, etc that will need to be sent along with product. please look at the simmarket website and understand this will be the basic goal of the webstore