mine comes with projector halogen, I'd like to go with HID.

will it be too bright if I change them to HID bulbs? I don't want to blind on coming traffic. Are my headlamp housings suitable with HID bulbs ?

and if so, is it easy to replace with HID bulbs ?

 

HID lights=xenon arc bulbs + ballast

You will need to obtain OEM headlamp housings and other parts to install them. If you have everything, they are plug and play from what I understand on the W211.

I do think you have to remove the front bumper to install them.

 

There is a sticky on headlights, bulbs, HID's etc in the W211 forum. Perhaps read through that?