The plugin cannot modify any snippets created by WooCommerce. However you can completely deactivate the generation of snippets created from it. Then you can re-create the products snippet on your own. In version 2.2 the plugin has a partical WooCommerce support. So it might be that you get in trouble by creating snippets for variable products with multiple prices, for example.
Yes, there is a built-in support for it. However please note that WooCommerce creates Rich Snippets on its own. My plugin gives you the opportunity to remove those snippets so that you can create your own.