The shop module tempaltes have been broken down into small, reusable parts. This allows a greater freedom of customisation.
Here is the heirarchy of templates:
Getting the cart in templates
For convience, $Cart is available on any template for a Page_Controller, or sub-page type.
This is provided by the ViewableCart class, which is an Extension for Page_Controller. The Cart template function also handles recalculating the cart, just in time for use within templates.
Customising Order template
Note that if you customise Order.ss, this will change how it looks in the back-end. If you need the admin template to be different, update Order:$admin_template to your new template.