On the product listing page the product name is a hyperlink so it will pick up the anchor style from the css in your skin.
On the product details page the css style that controls the product name is "SmithProdTextLrg"
All the buttons in the cart are image buttons and can easily be changed to any image you like. The image buttons are stored in a sub directory titled "\images" under the module folder in the "\DesktopModules" directory. By using file explore with the thumbnail viewer locate the button you want to replace and copy over it.
If you are running multiple carts in the same DNN install please refer to the following forum post for instructions on how to style the cart per portal.
How to style the cart per portal
For more info on styling the cart refer to page 183 of the cart users manual http://www.smith-consulting.com/Portals/0/docs/smithshoppingcartmanual.pdf