N00bs!!
Here's how to decompile scripts:
1.) Open your UT2004 folder in Windows (or your OS)
2.) Open UnrealEd (not XMPed)
3.) Click on the button that looks like a chess pawn at the top. It should open something called the "Actor Browser."
4.) Click file --> open
5.) Select your UTXMP.u file
6.) Hit "Open"
7.) Select any actor in your actor browser and double click on it
9.) A window with a blue background should appear with code in it
10.) Hit File --> "Export All Scripts"
11.) Wait for it to finish its stuff
12.) You still have your UT2004 folder open in explorer, right? Take all the new folders in there and stick it in a new folder called "Reference" or something akin to that.
13.) There should be a folder inside "Reference" or whatever you called it that is called "UTXMP."
14.) Open that folder
15.) Open the classes folder
Therein should reside all the raw .uc files that FMI originally coded, and all the information you'll need to make a mod