iPod erasing songs

[TouchdownQ]

I have a video Ipod (80 gig) But the computer that has my itunes account has been disconnected from the internet due to relocation. I was going to set up a new account on my newer computer so I didnt have to wait so long to get new songs, but when I plugged it in it says that my ipod is synced with another itunes library and only one library is acceptable at a time. The asks me if I want to "erase and Sync" or "transfer purchases" If I do the second one will everything on my ipod be on this account? I am so confused. Which one do I choose to keep my songs and will I be able to set up an account on the new computer? And there are no songs currently in the new library. Thank You