Replacing E320 Fog Lamp Lense

The lense for my passenger side fog lamp on my 2004 E320 has been broken by a rock, and needs replacing. Can anybody give me some tips on how to do this? Can I access this via the bulb replacement door under the car, or does this require that the bumper be removed and hence a trip to the dealer?

thanks, Simon.

My 1999 E320, you just do through the lamp replacement door. Pretty easy.