replacing the radio in a 2000

I was wanting to replace the radio in a 2000 cavalier since the one in it doesn't work. Crutchfield said I need a adapter retain the factory door chimes?? Do I need this adapter, what does it do, and is it necessary? Any insight would be helpful!!

There is a bunch of info related to this here: http://www.automotiveforums.com/vbulletin/showthread.php?t=321030
Look for the section on class II Radios in the first post. Good luck!

I went to walmart and picked up a GM2000 plug for around $40 and you can use any radio.