You should check out our tutorial on using Firebug. If you aren't good at CSS it can be a real life saver: [link]http://www.webassist.com/tutorials/Using-Firebug[/link]
There is an extension that comes with Data Bridge specifically designed to help with dependent dropdown lists. The feature is called "Dynamic Dropdowns", so you should find that in the help documentation and it should tell you the steps you would need to follow to make that update.