my iPod cost £300 and is 20GB. Apple say thats 10,000 songs but I say closer to 5 (I like high quality). Size roughly 2 1/4 inches wide; 4 inches long; 1/2 inch deep. I'm sure the exact sizes are on apple.com.
As for finding songs: so long as you got them organised (correct names, genres, albums) its really not a problem. You can search on it but just scrolling down is easy enough.

