Do a search on "S500 Home at last"
Your car and mine are pretty much the same except for the engine size.
I struggled for several months with design flaws with this (W220) chassis.
Among other parts that were replaced, was the K40 relay. Once my mechanic traced several grimlins to this relay, my navagation and CD regained function.
You will need alot of patience with this car. I have been trouble free now for over a year.
Also, I caution you not to use the cup holder. Fluids that spill from this location will gum up the sensors in your transmission selector box. When the sensors can not detect which position your gear shift is in, the selector sensor may decide to put your transmission into reverse. This is worsed case senario. But it has happened.
I hope the info you find in my posts will answer alot of questions down the road.
