Wordpress Plugin Development : Customization

I already have a custom plugin which basically shows a combination of all custom posts list. Please see the example image attached. It is pretty similar to the post/page list in wordpress. I like to add a Thumbnail column to this post list. What I like to do is to attach a hook to Publish/Save Action in a Post. Each time the user saves/publishes the post, a snapshot of the the preview page is taken (you can use any existing php libraries for the web screenshot) and use this as the thumbnail for the post list. I will need the development done for this in the next 5-6 days. Only bid for this if you know very well on PHP and Wordpress. Don't bid if you just know CSS and Designs as this involve advanced backend knowledge. Also in your bid, please describe what you understand and how you will execute this!