yes sort of

the ipod works as standard as a synchroniation device so as you say you have a library and you just copy the bits accross

what you need to do is in itunes right mous click the ipod (when its connected )

select options

then you somewere in there maybe 2nd tab it will be set to automaticall manage music

if you set this to manually manage music you can copy tunes to the ipod as you wish and delete them off pc but then you will allways have to manually add songs onto you ipod one by one