There is a lot of discussion on
http://forums.mbnz.org/forums/ about Xenon lights. Everyone enjoys the change.
Re retro fitting the MCS into your '99 it would probably be less expensive to install either a Garmin GPS or just buy a '00 ML than to retro fit the MCS into your '99. I was told that the price of the base unit, excluding all options (phone, GPS, CD player, wiring harness) was about 5K. And really, IMHO, the MCS it is by far the most idiotic "feature" offered on the ml. It adds little to the driving experience unless you want the uncompetitive (read that outrageously) priced phone and GPS, at well over US *$1000* each.