shop recommending replacement of master cylinder and brake booster but I just need rear brakes

Hello, I'm Danny.

Here is a tutorial on how to remove and replace rear brake pads and rotors:

https://www.2carpros.com/articles/how-to-replace-rear-brake-pads-and-rotors

Here is a youtube video from our site on how to compress the rear caliper piston when performing a rear brake job:

https://youtu.be/j8YwfSKEzZo

I've attached picture steps below on how to replace the brake pads and rotors on your vehicle. Hope this helps and thanks for using 2CarPros.