Deleting songs

I have my iPod touch 16gb almost to capacity. What I want to do is delete my main library on the iPod so that when ever I sync it, it just updates my playlists and podcasts. Is that possible?

Also, When I plug it into my black macbook, it wont recognize it anywhere. I think it's because I clicked the wrong answer to a question when I was restoring an older ipod to its defaults.

Have you tried creating a playlist called ipod

Then move just the stuff you want on the ipod in to the new playlist

Then click on your ipod and in the music preferences choose sync music: by selected playlist

You can create a similar thing for podcasts