There were at least 4 sets of different solutions with full source code available on the first page of the google search. if you need more help than a complete set of source code from a working mp3 player then you might need to lower your sights a little bit and choose a less demanding project?
If it's for a course most of the marks will be for the analysis / requirements / design portions of the problem anyway. Do you know how an mp3 file is structured, how you would go about decoding it into playable sound output? What about other sound formats? The ogg vorbis ones are MUCH easier to decode than mp3 / wmp formats
Visage, havent we seen a bit torrent client here before as well?
HT