'98 ML 320 - My head light is out. Is this a matter of bulb replacement or do you have to replace the unit?

Its just a bulb, a little cramped on drivers side. I would get the bulb and then remove the old, dont touch the bulb glass use something that wont transfer body oils

you may just replace the bulb, just look for a store, most of them sells the whole Mercedes headlights assembly. one more thing, just be very careful in replacing it, see to it that it is properly installed. good luck..

The bulbs are H7. I just found SilverStars at Walmart, and they are in local autoparts stores. The instructions for changing them are in the manual. Just make sure they get seated properly as it is a little tricky.

As said above, don't touch the glass of the bulb with your fingers - hold with a tissue or thin rag, or similar.