You may not need to lift the rear to troubleshoot your problem. If you can take off the left muffler it will help. Use a pair of pliers or a big screwdriver for a lever and pry on the caliper to reseat the piston in the caliper. If you get it in the right place it shouldn't take much force. It can be done without schratching or gouging any parts. If you can do it the sound should have changed when you roll it around the garage. Now step on the brake pedal and compare the sound again.
If that doesn't work for you take it back to another dealer. Lift it, spin the front and the rear, they should sound the same. Work the brakes while it's lifted and see how the noise changes.