I have just installed Linux on my 17″ Apple PowerBook G4. This page is an attempt to document what I needed to do to get everything installed properly.
The Airport Express needs firmware in order to work. Luckily I had an old Netgear PCMCIA network card that I could use to connect to my wireless network while I downloaded the appropriate drivers. What worked for me was running the command:
sudo apt-get install firmware-b43-installer
and then rebooting.
Sound worked straight straight away, without any additional configuration.