This script allows you to easily replace your old MP3s with new AACs from the iTunes Music Store. Just select the old and new tracks and run the script. It copies the playcount, playlists, and rating from the old file to the new, removes the old file from the library and places it in the trash.
OBLIGATORY WARNING! Because this script has been designated as a "Retro Script" there is no guarantee that it will function as described and may even corrupt or destroy data.