I need help updating my I pod!?

Hi, I am trying to update my i pod using i tunes and I am having some trouble. If i update my i pod will it delete all of my music? If so, how do I prevent this from happening? My computer crashed a while back so I have music on the i pod that isn't in my i tunes account. Is there a way to save or backup everything from my i pod to the account. I don't care if the music stays on i tunes or not, as long as it is still on my i pod. I don't really know a lot about i tunes. I just know how to put music from the CD i bought into it, then to my i pod. I have never updated the ipod, but the old version is getting kind of outdated so I think it is time.

Thanks for the help!!