Incorrect I'm afraid. The Aux socket was only added to the Boost stereo in 2003. You do however have a CD changer socket.
I had one of these interfaces from Mikey at
NewMINIStuff.com on my 2001 headunit. Plugged into the back CD changer socket. Cable routed to pop out under the toggle switches, with mp3 in cup holders. My current ipod sits in the cubbie between the steering column and the door.
NewMINIStuff.com
Stereo removal instructions here
NewMINIStuff.com DIY Guides 
