To change the Add to Cart: to something else, using your templates and overrides you change the language file:
/includes/languages/english.php

and set the:
Code:
define('PRODUCTS_ORDER_QTY_TEXT','Add to Cart: ');
to read something else ...

To change the shopping_cart display ... you would again use your templates and overrides to customize the file:
/includes/templates/templates_default/templates/tpl_shopping_cart_default.php

and change the parts you do not wish to see ...

To change the checkout_confirmation ... you would again use your templates and overrides to customize the file:
/includes/templates/templates_default/templates/tpl_checkout_confirmation_default.php

and change the things you do not want to see ...