MC will "natively" play Audible files if the computer is activated to play Audible content. If the comupter isn't activated, MC will pop up a dialog to activate the computer. (If this should fail you will have to use AudibleManager to activate. Note: iTunes is a better utility for activating your computer for Audible playback than AudibleManager.)
MC will transfer Audible files to any device that supports Audible (aa) files without authorizing or activating the device. In order to play the files on the device you will have to use AudibleManager to activate the device once (MC can't do this).
We have had no problems with Audible files on the Touch.
Audible files can't be converted.