There are many things that are fairly straight forward right now, particularly since the modding community is so open with sharing what we've discovered as yet... but some things are nigh impossible, lest you be extremely well versed as a programmer. UI re-construction is one of those things. Hopefully the modding-update that Haemimont has teased in this past week will address this issue head on, allowing us to move elements, access the various information fields, alter the build menu and add new fields, icons, and text more easily.
Wouldn't be a moment too soon, either, considering what I'm presently working on myself!
Sorry for the disappointing news! I can tell you this, though: use of custom graphics to design a custom UI is well, well over my head... even following the code of others. It's just a highly complex endeavor.