My 4-matic light was on constantly. Also, if I put it in reverse and turned the wheel completely to the right, the entire car would shake. I took the car to my Mercedes dealer and they want $4,900 for transfer case and hydraulic pump. Should I take the car someplace else and install used parts? Can I just turn off the 4-matic and keep driving safely? The car has 123,000 miles. Any other suggestions? Thanks.