will music mods work if i just replace the existing .OGG file with another one? (say i replaced ANOTHER HIM with an edited OGG file in the same place that the original was in)

yes! just remember you cant mod mansion.ogg and cyber.ogg

Yes and the reason you can't replace "A CYBER'S WORLD" or "Pandora Palace" is because those tracks sync with the gameplay, meaning it would be affected if you modded the song.