Is there a way to put up an ecommerce site onto a Facebook

Hi,

Is there a way to put up an ecommerce site onto a Facebook tab? Ive seen it done before.

Secondly, were putting up a site using the Marketplace plugin. How easy is it to integrate a payment system? What the best theme to use with this plugin?

Lastly, does it have features which I can optimize it for search engines?

Thank you,
Virgil