i think currently you're stuck with burning the songs to cd and then reimporting them as mp3.
I was about to agree with Ian... BUT if you change your import preference to MP3 instead of of AAC. Then under the advanced menu you should have the option to 'convert selection to MP3'.
Cheers
(BTW this would only work with unprotected AAC files i.e. ones not purchased from the iTunes music store.)
Awesome! Thanks :)