There aren't really any aftermarket calipers for the car, only "rebuilders". Stay away from 'Rebuilt' brake componets unless you know the person that does the rebuilding & trust them w/your life!!
If the brakes did overheat as described then replace the rubber brake hoses & flush the brake fluid as well as the rotor(disc). you might find that the parking shoes are also damaged. NEVER put off brake work!! Stopping is the most important thing that your car does.

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MERCEDES BENZ MASTER GUILD TECHNICIAN
ASE MASTER TECHNICIAN
27 YEARS DEALER M.B. TECH
190E 2.3 ITS RACECAR