Is there anyway to replace the quake soundtrack to your choosing? Because I am curious.

EzQuake isnt able to do that but any modern single player client like Ironwail can handle that. Create a music folder in ID1 folder. Copy your music into it and load it with /music yourtrackname. Alternative you can name your tracks like the original tracks track02.mp3 track03.mp3 ..... track11.mp3 and the music will load when you start a map.