mallot on "[Plugin: WooCommerce - excelling eCommerce] Customizing WooCommerce/Mijireh Checkout CSS"

I'm using Mijireh Checkout on my WooCommerce site and "slurped" the page to bring the checkout page into the active theme's design. I'd like to make a couple of minor changes to the Mijireh CSS but can't find how/where to access the Mijireh CSS. Is this not possible?

http://wordpress.org/extend/plugins/woocommerce/