Yes it is possible. A guy over my.is did it. Here's the link: http://my.is/forums/showthread.php?t=317250
I hesitate to ask how much he paid to add that, it looks great though. Probably less work to trade the car for one with Nav/ML. Oddly enough, my 250 has Nav but no ML.
I just froogled, it came out $1500 for the unit. You might want to PM him for the total cost!