need some help with logic express 8

I am importing a file that I created in Garageband and saved as an MP3. I want to edit it in Logic Express so that the audio quality is better with compression. It was created as a stereo file, but when I edit it in Logic Express and export it as an AIFF file, somehow it keeps getting converted into a mono file, which is no good. Can you help me figure this one out? Alternatively, some way of editing and compressing the files directly in Garageband would be preferable, but I don't have the latest version.