2002 Pontiac Grand Prix Rear Brakes

When the brakes are applied, I can hear a grinding or rubbing noise, which sounds like it's coming from the rear of the vehicle. I'm guessing there may be an issue with the brakes. What it the easiest procedure to inspect the brakes and how do I know if the brakes need replacement? How difficult is the process of replacement? Will I need any special tools? Is there a website that I can visit that will provide photos or illistrations?

Thanks
Tom Leigl