Hello Ryan,
This is possible but however not supported by iTunes. Basically you have to copy or "rescue" the music on your iPod using a 3rd party software such as this:
http://www.kennettnet.co.uk/musicrescue/
The above software is free and fully functional, but it will nag you to register the software by purchasing a license. There are many other available programs designed to do the same thing, and can be located by searching "sync ipod to PC" through google.
The software will copy the music back onto your computer, and can then be imported back into iTunes.
