Are you on a pc or mac? If your on a pc and running vista, go to the folder that new file ( the one you already converted to AAC and changed to 30 seconds in lenth)
Look up in the top left corner and click, Organize> Folder and Search options> View>and uncheck hide file extensions. From there you can edit the file name by clicking rename. Then just click the file, and it will open in itunes.
That's all if your running vista.
- Muffin