Hello lurkist,
Well you need Mpega. MakeCD then can turn mp3 to AIFF.
But personally I would recommend mpdecode.
A small utility which converts mp3 to AIFF.
A lot of times conversions with MakeCD got glitches and with mpdecode I never encountered these glitches in sound.
You can find these utils on Aminet.
Good luck! :-)
Spidey