For those of us that have the xenon D3S headlight bulbs, don't be talked into having to remove the bumper to replace the bulb. I just watched my mechanic access it through the fender well. He put the car on a lift so he could stand in the fender well after he removed the wheel. He removed enough of the bolts holding the plastic inner fender such that he could pull it back and hook it behind the caliper in order to get it completely out of his way, All but one of the four screws holding the cover on the back of the lamp assembly are completely accessible. The one screw that is under a section of the body structure is the reason for the argument to remove the bumper. Some how he figured out how to get a torx bit with some tiny ratchet on it. Apparently, there is just enough clearance to extract the length of the screw. Once, the cover is off, the bulb and it's connector can be accessed. I was charged15 minutes labor and full retail price of $86 for the bulb.

 

I notised the opening on bulk behind of headlight too, but figured that the working time and effort is same in both ways. On my opinion the differense are that when headlamp assembly is removed there are less risk of misposition the bulb. By user manual the opening are for turning the lever of low beam adjust for left / right side driving. (EU vehicles)