OpenBiblio

Hi! Am fairly new to openbiblio. I'd like to know where I can have references on how I could modify the user interface. I am expecting that presentation is separate from content -- or not. No, I don't have a lot of time to dwell on this (maybe 2-4 hrs a week) is all I got to figure things out. I want to use CSS to manipulate the displays. I hope I'm not asking a stupid question here. I like this application -- simple and effective.