You can go to the Options -> Mods menu screen and click the file path to find the mods folder
Navigate to the mod folder (enable show hidden files and folders to see AppData)
Once in the mod folder, create a folder a name it "My Music" or something.
Copy (NOT CUT) the Sound folder from the SoaSE root folder and paste the folder into your mod folder.
Now you can edit or replace any event sound or music track in the ...\My Music\Sound folder and will play in game once you enable the mod.
I have 4 soundtracks for easy loading as a stackable mod because I to get tiered of the same music playing.
There are a few different sound editors that can convert to .ogg files. SoaSE uses 128kb/sec, 441000 stereo for music and 128kb/sec, 441000 mono for event sounds.
WinAmp is a free player that will play .ogg files.