To see if HAL & other shit is working:

dcop kded mediamanager fullList

Amarok will not play MP3's until you download and install the newest version of Xine.

See the Xine page for more information.

Even after Xine is installed, you still have to tell Amarok to use the "Xine" engine (some new "feature") instead of the default "yuauap" engine before you will be able to play MP3's.