this is super easy all you need is a pair of needle nose pliers!!!! you just need to push the pin out and the caliper comes off here is a link to the how to. however if you are going to change the rotor then you need a t50 torx bit.
http://www.cougardb.com/info/pdf/Rear_Brake_Install.pdf
Yes
i need a diagram on how rear brakes are assembled
Remove the tire and wheel from your 1999 Mercury Cougar. Remove the brake spring and the break caliper. The brake pads will come off. Reverse the process to install the new brake pads.
you must repalce the whole hub since it comes as a assembly.
Yes.
disc brakes - front and rear
Brakes come in two types: disc or drum.See "Related Questions" below for coverage of both types...
just replace the rear brakes
how to replace rear brakes on 1972 f600
This is as complex procedure. I suggest you buy a repair manual if it is not obvious to you, and you don't have experience.
Conventional drum brakes.
drum brakes