Once you are satisfied with your test site (on your site or local installation), you can import the site to your live one. Follow the instructions on the links I quoted.
Yes, you can integrate WebCommerce/ Shop interfaces as usual, though I do not know what software you are using. You can also use a plugin. See the link below, choose one, install and activate.
http://wordpress.org/extend/plugins/search.php?q=ecommerce