To play a song, when you're in AudioPlayer press the Play button to begin playing the first song.  The first thing you will want to try is the hidden "waveform" plugin.  While playing a song, tap on the "S" in "SoundsGood" at the bottom of the screen to change the bottom bar to a moving waveform; tap anywhere on the waveform to turn it off.  You can see a screenshot of the waveform in action during "Enter Sandman."  Yes, Lars, I own the CD.

Use any of the screen icons or SoundsGood hardware buttons to change songs and volume.  All of the options I have mentioned are available on the main AudioPlayer screen.  Use the up/down slider to adjust the Volume (you can use the wheel on the module or the Visor's Up/Down buttons as well).  The horizontal slider can be used to skip to a particular point of a song.