Nothing much special to this job. You do have to remove the trim panel under the headlight, don't forget the hidden screw at the inside corner under the side marker. The whole assembly is in turn held to the body by four bolts - 2 top and 2 from underneath. The are an additional three bolts if you have headlight wipers.
The "door" on these US lights is the fog light lens and it is held to the assembly by four plastic clips. The head lead lens will have to be completely replaced, I don't believe the lens proper can be separated from the body although some say it is possible.
Now would be an excellent opportunity to convert to Euro lights. For what it will cost to replace the door and lens you can buy a quality after market set of Euros. Update the look of the car and best of all get the lighting you deserve.
Here is how the Euros look;
'73 280SEL 4.5 (9/72)- RIP
Only 8,173 units built from 5/71 thru 11/72
'02 CLK320 Cabriolet - wifey's mid-life crisis
2012 VW Jetta Sportwagon TDI...at least its a diesel
Non illegitemae carborundum.