Hello there Luis Vasq,
I am sorry to hear of your lost iPod. Your iTunes Store purchases can always be downloaded for free when you sign into your Apple ID on your computer, or an iOS device. This article will help you with that.
Downloading past purchases from the iTunes Store, App Store, and iBooks Store
If you are going to re download your purchases to your computer, you can use this article to download them there:
iTunes 11 for Mac: Download previous purchases from the iTunes Store
Your other media that was imported from CDs or other sources, would have to be re imported to your iTunes Library. This article will help you import your CDs and/or import media from other soures you had:
iTunes: About the Add to Library, Import, and Convert functions
There is a service called iTunes Match that allows you to store ALL your content, on the Cloud for download to your devices whenever you need named iTunes Match. This may prevent you from losing any content in the future, should something like this ever happen again. Here is some more info on that:
iTunes Store: Subscribing to iTunes Match
Thank you for using Apple Support Communities.