You should open the hood and look at back of the headlight. You will find a cover to remove, or otherwise look for access to the bulb. I have not seen an MB with non Xenon lights that requires any tools to change a bulb.
Do not handle the bulb with your fingers. The oils from your fingers will reflect energy back to the element and the bulb will burn out quickly. You should not have to touch the glass of the bulb, but if you do, use a clean, dry paper towel.
There is no need for readjustment after bulb replacement.