well, first of all, VENTONES
is a site where you can make ringtones from mp3 files. That is what you need. It won't work with Itunes files directly, because you need to convert them into mp3 files first.
For itunes files, you can convert them to mp3 files,
by making a cd out of the itunes songs, then converting them to mp3 format with Windows Media player. Do a search online on google for more info on that.
Once you have the mp3 file, upload it to Ventones
and pick what seconds of the song you want,
Since you dont have internet, save the file you make with Ventones to your pc,
and then , since you have bluetooth on your phone, you can buy a bluetooth dongle for your pc, it costs like $15.
Then sync the pc and phone up via bluetooth, and trasnfer the ringtone to your phone's memory.
Or just buy a data cable, and transfer it that way