Lots of questions...but you have the older model W140...mine (being a 1996) removes easily with the radio removal keys...it takes just a few seconds. After removing the unit, there's three screws to remove and some pieces snapped together. From there, the back side of the buttons are exposed with all the broken parts. I glued the tabs back on, then reinforced them with some old cut up credit card plastic...doesn't sount pretty, but it worked to get the buttons operational. It didn't help the software problem however...as you can see from my earlier posting.
Jim F...If I had only known about this site a few years ago, I would've saved a ton of money. MB likes to keep the W140 a big secret. I'll check your sources.