If your just doing a cosmetic mod there shouldn't be any UI coding. Look at the files BackdropFrontEnd.dds, BackdropInGame.dds, Buttons_Backgrounds.dds, Buttons_Interface.tga and Skins_Tech.tga.

And I am really interested to see what you come up with. Good luck

As a mod you can overlay the existing UI by modifying the files listed. This is what I'm thinking about doing for my mod by adding an optional overlay for those that want it for the different races.

In your case a Advent UI Mod and a Vasari UI Mod would be cool.