Depending on your phone you should be able to use an mp3 as a ringtone.
I just got a Nokia e71, and Nokia has a program to transfer data. Is asks me if i want to convert the file to an mmf. I do to save space - the quality isn't lacking. I think it is called Nokia PC Suite. Drag and drop - convenient.
If you don't have a Nokia I can't help you. Sorry bud.