I need help with changing game sounds.
 

I was looking at the addon Modern Warcraft and had an idea to change a few sounds to my personal preference, but I wasn't sure how to and where I can locate those sounds.

The sounds I wanted to change are:

Level Up
Achievement
Dungeon Queue
Battleground Queue
Battleground Start
Battleground End
(Maybe even the music that plays during BG's)

That's all I can remember for now.