A long time. If you have an ear for music, you can do it. Just keep playing a short section at a time over and over again. But if you can't distinguish high from low.... forget it. I have done it myself and can usually copy a song within 3 takes(melody, bass line, chord progression based on the first two), and I've been playing piano all my life. Maybe you can ask a friend to help you out?
Hope this helps.
[Edited by Brahmb on 08-05-2000 at 09:11]