How popular are multiple disc CD changers? It seems that they would have been replaced by all of the available MP3 player setups or just MP3 CDs for that matter. Both of which can hold the content of numerous CDs in one place. Though now I assume that you can load a CD disc changer with MP3 CDs and have a huge collection of music in the CD changer. A CD changer does offer the convenience of not having to change a CD while driving, but then again so do the MP3 player options.
This video shows the basic hookup of a CD changer in a BMW 5 series. This car is already wired for a CD changer, so the set up work was already done for this installer.