Mono means 1 channel - Meaning you get the same sound coming from both speakers
Stereo means 2 channels - Meaning you get different sounds from both speakers at the same time---eg; Vocals coming from the left speaker and guitar coming from the right
Mono and stereo have no affect on sound quality what so ever.
All the music files in the game are recorded at 22,050hz meaning your going to get sound quality half as good as a CD but each file are also 16bit which makes up for good sound quality.
Each track from the game run from anywhere between 96kbps to 172kbps, the lower the kbps rate the scratchier the sound becomes.
Just thought I'd add this information to people who are tearing their hair out about getting the music files off the disc and making them sound good.