Hi,
forum is not good place to learn Wordpress in general.
But the rules in theme customizations are quite similar to Joomla! anyway.
Our framework also include option to enable override.css file which is also "hidden" in theme folder.
Template options -> Advanced --> Use the override.css file [yes]
So first step is always this same using firebug check which class you have to change, test online and do it in css file.
I'm new to wordpress, having used Joomla for years.
I've got it - I'm on this same path as you. But I still try to avoid WP for big projects I use only for small & simple one.
