Rotor, Caliper, maybe brake pads too and you'd need the bracket. So around $400 if you can get a deal on it all.
If it was for me and I wanted a brake upgrade I would do the 300zx 30mm aluminum bbk. But I don't need to especially since I just got the brakes done yesterday. Has some bite to it!
The parking brake actuator stuff is internal to the caliper. I'd have to see a cut away drawing or exploded diagram to really describe it acurately, but when you replace the rear calipers, all the parking stuff will be renewed, too.