Was thinking of buying a used SL600 2004 for $21k roughly. Just wondering the common things that break on the car and what to look for when buying it. Any advice would help out. Im a mechanic myself and I do have patience so I can work on it myself if need be. 2004 Mercedes-Benz SL600 Roadster, $21,900 - Cars.com

Said to have a new ECU upgrade and a shift module already installed. 68000 miles on it. Rear bumper cover replaced due to someone rear ending them at a stop light, not going fast apparently. Its the sport package with all the trimmings on it. Comments and any advice would be nice. Thanks