Has anyone replaced the rear shocks on an 1998ml. just replaced the front, the top shock nut was rusted and had to be cut off to get the shock out. They used ot put covers on the shocks (years ago ) so the nut would not rust. I have 155,000 and the rear need to be replaced. How should I proceed, buy the whole unit together or just buy the shock? How is it to install, do you need any special tools ( spring compressor), Is the top nut hard to get off ? Any advise would be helpful ? I used Bilstein on the front.