Sorry its me again 

You can change any sound u like in the game. First, get the game to know about ur sound, then use the new sound's GUID in .LAYOUTs

Get it into the game:
- safest to use .wav files but .ogg works too
- define the sound. Open up any of those .DATs in MEDIA/SOUNDS/...  and u should readily see how its done, where to put the sound file, etc.
- like any other DAT make sure your sound has a unique GUID and NAME

Use it in the game:
- different usages will call the sound in different ways
- in skills, the layouts will call it by GUID (altho in GUTS u just select it from a dropdown
- animations call sounds directly from the .ANIMATION files of the model in question. See those [KEY] lines with like NAME:EFFORT in them? "Effort" is the NAME of that grunting sound your char makes and the anination is calling for them at certain frames.

Try it out and let us know if u need more inputs

Edit - i think ima make this into a short tut with pics and stuff