Hi,
4859589 - I can implement the chat system. I have one suggestion also, if we implement a comment system instead of chat, it will be useful for other users also, and the seller will also don't need to reply to the same question every one asks. Also we can go one step further if we implement facebook or discuss commenting system for this, so when a user makes a comment it will be notified to all his facebook friends, and the page url will be spread thus increasing visit to the page and site.
Let me know your thoughts, Waiting for your response. Thanks.