apacheco

First post here, any advice would be greatly appreciated. I was intending on performing a brake job for my friends 17 gle350 in awd. I successfully disengaged the parking brake and put the rear calipers into service mode, however I closed the door at a point in the process, returning the caliper to its standard mode and engaging the parking brake. After this it would not go into service mode and the digital dash read “parking brake” “see owners manual”. I then looked at the caliper that was off the rotor at this point, and the piston had been completely pushed past the seal, I’m at the point of; A attempting to push the piston back in the caliper on my workbench; B have the car towed to a shop; C order a new caliper and hope there are no issues with programming and software regarding the electronic parking brake module; or D, sourcing a used caliper from a partout and take the risk for money saved. All in all I feel terrible as it’s not my vehicle. I feel responsible of course although I am suspicious of this being a parking brake malfunction.