Modification of a Joomla Site to Add a Shopping Cart

I have a Joomla site. I need the following done in joomla Part 1 A shopping cart for products. a) A registered user should be able to register a product with product name, product description (3 paragraphs), cost, and some photos (to appear in the products profile as demo photos). b) The project is listed under existing market categories. c) Any registered user can select a product and add to cart. d) On checkout, should be able to show the clients that paid and those at invoice stage. The site to be modified is (To see the site you need to work) [liq uid sys tems tech nologies . co m] Part 2: a) I need a way someone can post a project ( a detailed form on the project specifications); c) Once project is posted - different users can provide cost of doing the project (like bidding). d) The person that posted the project can allocate one user to do the project, and pay the amount bid by the developer.