I'm not sure about this, but if you bought all the music from iTunes, you should be able to re-download them with no extra cost. If it is from another music store, you could try to re-download them if it won't cost extra. If it would, you can contact them, explain your situation, and they might let you re-download all of your previous purchases. If it was ripped from CDs, then you could obviously re-rip them.

Also note: The iPod touch will not show up as an external drive no matter what you do. You can't just copy the hidden music files off the drive like you can with all the other iPods. So if that was what you were planning to do, I do not believe it will work.