Ebay like " shop " feature needed + SEO and few changes

I own a Freelance website close to Elance and I would like add the following feaures : - “ store facility ” like on Ebay: users should be given the ability to upload into their stores their files/ ready to buy hours of services / tutorials / papers / studies / creations etc…. they wish to sell. A specific search engine to browse among those files should be created. Users should be able to control their store in an easy way. A list of categories made to help narrow down user’s searches will be given as well. In order to give visitors a “taste” of what they are about to purchase, once users click on the title of the essay/product/services, they should see a brief abstract of the document or the services they are going to buy, language and format (.pdf, .doc, .rtf, .JPEG, .raw etc…), number of pages/words or synthesis along with the CV of the author ( he/she can be an individual or a company ), his/her ratings and feedbacks. Visitors should be able to acquire these items trough a “download it now” button for documents and trough a “buy it now” button for services. Users should refine their search only trough the keywords they will enter into the search box. They should be given the ability to see the keywords results trough the following options : Ascending/Descending prices or according to the seller’s ratings. There are some small other changes that need to be done but they will be discussed with the choosen professional We also require to have full SEO service for the promotion of our website, kindly make sure to include it in your price quotation.