So this question has probably been asked before, if so please dont hesitate to re-direct me to the thread that explains how to help

Over a year ago I won an 8gb Ipod touch but did not own a macbook or a computer of any kind for that matter. I had a friend load his music on to it from his computer and he has sinced moved overseas. However, after settling into a new condo I finally bought a macbook pro!! I want to use my Ipod touch to upload music from my new computer, however I do not want to lose the music I already have. Before I go plugging it in and trying to do it myself, I was wondering if someone could tell me how to keep my existing Ipod music as well as update it with my new music from my new computer. I hear there is a software called music rescue or something like that...

any help would be appreciated
TIA.