So I just updated itunes, and I open up itunes to see all my music was lost. It's still on my PC though.

Is there a way to restore it rather then digging up all the thousands of songs one by one and adding them back?

I'm also planning to buy a new PC soon and sell this one. I don't want to lose my library over this. Is there a way I can put my songs on itunes simply by using my ipod?