How can I reduce/clean up the page template in GridMarket, and not loose my work after a theme updat

How do I create a new user page-template for my network to access?

How do I customize the networks root page-template for the GridMarket theme? In the home page, I want a global-product list in the content area, and a sidebar with a few widgets.

1. I would like to reduce the amount of space comments take up on the page template, or
2. I would like to move comments to a widget sidebar.

Thanks.