Hey Michael, I have kicked around the idea of moving my ITunes but have been worried about messing future downloads up. I have heard it is easy and also heard it is a nightmare. I would highly suggest you back them up on dvd b4 doing this. The files on ITunes are relatively small and don't take up a lot of room. I have about 1,400 songs on mine.
As for moving pics. Oh yea, I moved about 40 gig to my external and reclaimed most of my HD back on my laptop. If you do it, PLEASE post or email later and tell us the ease or otherwise of doing your ITunes!! cd