iPod and iTunes question about updating

Hey,
When I first got my ipod and installed itunes on my computer, I didn't know that I should have checked the box that read "Manually update song list". I instead left it on "Auto update". My dad bought a nano, and so I spent the last week putting 315 songs onto it, and some of the music is something that I don't particularly care for. On my dad's ipod settings, I set it to manually update, which allows me to drag what I want into the ipod window.

I have tried changing my settings on itunes and it says that my preferences could not be changed since my ipod could not be found, even tho it is plugged in and visible in itunes. I also tried to reinstall itunes, and it just keeps ejecting my cd. What should I do so that I can edit/delete what I want on my ipod? Thanks guys.