This should work for both Xine and MPlayer.
All as root:
tar xvfj all-20060501.tar.bz2
cp ./all-20060501/* /usr/local/lib/codecs/
cp ./all-20060501/* /usr/lib/win32/
chmod 755 /usr/local/lib/codecs/*
chmod 755 /usr/lib/win32/*
Both Xine and MPlayer will now be able to play everything...
Getting Xine and MPlayer:
Don't use source code for apps like Xine and Mplayer.
They're dependencies for other apps as well, so stick with RPMs.
I highly advice to use the SMART package manager instead of Yast.
It will come with many extra sofware repos including Packman and Guru:
XMMS with mp3 support:
Install the xmms-mp3