I use
Firebug to figure out where things are located in the CSS; that's probably the best option for you as well. Firebug will show what the code looks like and give you the file location and line number that each specific section starts on.
The majority of the appearance adjustments in the Vertex-based releases are pure CSS and don't use images at all, so there's a good chance that you only need the PSD as a reference to help you make adjustments to the CSS.