I used:
phptemplate_uc_cart_block_content() for the block on the left side
phptemplate_uc_cart_view_form() for the "view cart" page (original theme_ functions in uc_cart.module)
phptemplate_cart_review_table() for the review cart on the checkout page (original in uc_cart_checkout_pane.inc)

This pretty much did everything we wanted...