Product "Forum"

Visitors to the web site select from a list of products and fill in a form with their email address. We get notified that a request for more info on the product has been made. We reply to the request 'on-line'. The visitor get an email notifying them that a reply has been posted with the URL to the reply page. They can revisit and request more info which we can post a reply to. We will be notified by email when a visitor replies to our last comments. The page records all comments from us and the visitor. The visit can then click on a BUY NOW button which will notify us they want to buy the product. We need to be able to add, remove and edit products through an admin console. Please give cost estimate and we can provide full details on request.