EQ2 UIBuilder & Interface Info
You can find the EQ2 UIBuilder from sony in a zipfile in the root of your Everquest II folder in a zipfile called UIBuilder.zip.
Unzip the files into a folder on your hard drive and double click on EQ2UIBuilder.exe. This will load the UIBuilder and you will see a program open up on the left side of your screen. You will then want to go to File >> Open and open up the eq2ui.xml in your %eq2%/ui/default directory. Then a preview window should load up and interface elements should be listed to the left. Across the top are tabs to preview each window. From then on your just need to play with the program to figure it out further.
In that zipfile is a doc called EQ2_UI_Customization.doc. Make sure to read through this file as it has some good information.