Havent seen this around so thought id write my first guide (Beware of the wall of text, it shall have the bunnys fly)
Needed programs-
Mywarcraftstudio
Xnview (unless you want to rename manually..)
In this im going to change the Female night elf sounds to Female human.
Start out by Loading up MWS and open Worldofwarcraft\data\enGB\Speech.mpq
Extract the human Folder thats marked.
Delte the male parts in the folder, you're not gonna need them, rename the folders Nighelf where it says Human, an example would be HumanVocalFemale -> NightElfVocalFemale
Start up XnView and go to the female folder Marks all the items in there, right click and press rename
in the middle of the screen, where you can read replace and i typed in Human in the upper line and NightElf in second line you type the same (changes from race to race ofcourse) Remember to set it on Case sensitive just to be sure
Now do the same with the rest of the files in the other folders
Start up MWS again, Extract some random mpq to get a Blp file. Put the file in the Sound folder You are going to make just after this then Press Pack - Create MPQ archive Name it something like.. Patch-s.mpq
Then make a new Folder named Sound and put a folder named Character in that, put your NightElf folder in that
Back to MWS you click import folder, go into the sound folder, and press the blp file you copied earlier or something else you copied to that folder
Press ok, press the + and delete the random file you put in the sound folder Press pack -> Save and close archive
Put the mpq in your data folder like the normal mpq edits
and youre done
Bare with me, this is my first guide so any good pointers would be nice and all