I need to take off my rear disc to get to my rear

you dont take off the nut in the middle! there should be 2 set screws to hold to rotor in place. the inside of the rotor acts like the parking brake drum. you will need to chalk the wheels and release the e-brake. they do sometimes stick therefore you will need to take a thick piece of wood and place it on the back side of the rotor and hit moderately with a hammer till it comes loose. it will then be necessary to pull off square due nto the e brake assembly inside. nothing too fancy however you will now need to retorque that nut to about 200-250 ft lbs. be careful.