Add-on feature

I like to add-on feature to my website 1) A seller post selling item where he/she can place a video demo about the products. for any users to view 2) users/buyers can make comments(small message board) about the products details: - video - seller can upload youtube video (or other video sharing) from my website. can be link or embed but it must be done by user itself. because space area concern the video screen must be smaller and the screen must be auto adjust. - comments - (message board) i hope it allowed admin to edit in case it been abused see attachment the display result and drawing of the add-on featured getafreelancer