How to create Store page just like in wordpress.com

Hello folks,

I'd like to create a store page (just like the one on the admin site of wordpress.com) and understand that I can use marketpress plugin (please correct me if I'm wrong).

My question is if I have a product/package listed in my store that allow X number of posts, how can I update the post creation limit after payment? Btw, I'm using post creation limits plugin to set initial post limit of 5 for registered user.