Wiring problems of the 2004 Mercedes Benz C230

This is a 2004 mercedes C230. Check engine light went on. I went to dealer within 15 miles of warning light coming on. I was told that there was an oil leak and that it had dripped over the wiring harness. It would cost $3,500 to repair. I have never missed a maintenance on this car. They said the this happens because of where the O2 sensor is located. This is a defect and design flow created by mb. They should do a recall to protect the wiring harness.