As to draining the oil on a ML, my guys have found a neat trick. One can take an old anitfreeze plastic container and cut it at about a 45deg angle. Place the bottle spout upside down and place the whole thing into the suspension about 5-10inches from the drain plug. When the plug is removed the oil jets almost horizontally into the side of the bottle and runs out the bottle's spout below the suspension vertically into a drain pan.
I was shown this when I decided to change my wifes oil myself. The tech sliced up the bottle in about ten seconds and not a drop got on the vehicle.
If you are servicing this car for yourself (not the owner it will have from 100k onward) I would suggest paying for an unrecorded oil change at half intervals. MB has already got in trouble for telling people they could drive that far with dino oil. The problems they were having are just put off by only changing to synthetic.
and... If you would like the transmission to go into the second k or beyond you better service it at some time also.
Since its highly unlikely that you will own the car that long, its risk free to use MB intervals.
Bosch Master, ASE Master, L1
33 years MB technician