Updating ipods

Yes.

iTunes syncs exactly what is in your library to your iPod.

If it's not in iTunes it will not be on your iPod.
You need to add you entire library back into iTunes if you want it all to sync.
Old songs which are no longer in iTunes will be removed from your iPod if you sync.

yes!  you will lose all your music, so be careful. you may want to set your ipod on manual mode if you don't want it to automatically sync with a new or an empty itunes library.

If you still have your music in your ipod, what I can really recommend is to put it back into itunes. Just download this tool, select your music and clic backup to itunes! That's all! It will automatically import all your songs, playlists, videos, tv shows, etc. and restore your library!

All you need is to get all music and other media files from your iPod back to your computer and iTunes. Simply use iBackup - iPhone/iTouch/iPod to Computer Transfer program to help you. I

t was designed to help copy all music, videos, photos, playlists, podcasts and more from your iPod to your computer and iTunes in the quickest and easiest way without any data loss. Then you can sync smoothly.

Just free download it to try. It works like a charm.