Kentuckycat,
Very simple to replace. Remove your rear tire, remove the 2 bolts holding the caliper on, remove the 4 allen bolts holding the rotor on, rotate the rotor so the mounting flanges line up between the rotor mounting tabs and remove the rotor. reverse to install. I also used some lock tight on the bolts to insure they don't come loose, just make sure you use the removeable type lock tight.
DadsZ400