An e-commerce site I'm currently working with also has storefronts on eBay and Amazon. When searching Google Shopping, their Amazon and eBay product listings come up but NOT their primary site's listings.

Can anyone shed some light on how to a) feed the main site's products to Google Shopping and subsequently b) have Google remove the eBay and Amazon listings?

Obviously, this would be a boon to business and hey wouldn't have to pay the Amazon and eBay fees associated with each sale.

Thanks for any help!