Retrieving Purchased Songs From Itunes

I know this may sound stupid, but I was wondering is there a way to get back my purchased songs from itunes. Reason I ask is I had to get another pc and reinstall Itunes. I have all my songs on my Ipod, but am wondering how to get them back on new Pc. And also I'm afraid if I plug ipod into new pc it will erase everything on Ipod. I'd die if I lost over 1500 songs. My new pc is authorized