Getting at source of code pulled by php

Hello,
I have added the simple paypal shoppping cart to my site and have been customising the css to suit. However, some of the elements in the cart itself (specifically the text alignment within the table that lists product, quantity and price) are styled with ‘element.style’; the style attribute is applied inline in the html, rather than in a stylesheet. I can tweak this through firebug to get the effect i’m after, but as the code is pulled by php from within the plugin, I don’t know how to get at it to edit it permanently.
Grateful for any ideas/ pointers. Thanks in advance.