if you know where your music is on your dell just bung it on a spare external drive and transfer over?
maybe make a copy of the iTunes folder in the music folder deleting the itunes library xml file as it wont be the same locations on the mac for your music. Backing up the iTunes folder also keeps any artwork you may have downloaded.
also go to %appdata%\Apple Computer\iTunes\iPod Software Updates in windows explorer and copy the restore file from there (saves you re-downloading if you ever need it)