I'm not sure what you mean by headlight doors, but swapping the USA headlight modules for European H4 modules is a bolt-on job on 124s and 201s. Illumination is vastly superior, but make sure they are adjusted properly. IIRC the left side cutoff should be 3" below the vertical center of the lens 25' out. The beginning of the 15 degree rise to the right should be dead ahead, and I think the fog light cutoff should be level with the vertical center of the lens.

I bought a set for my erstwhile '84 190E 2.3 and then swapped them into the new '88 190E 2.6 special order five-speed.

I recall I used the original USA corner modules with the turn signal and parking light bulbs. They are interchangeable with the Euro corner modules, and I just put a vacuum cap over the nipple for the Euro "city lights" function, which dips the headlights a few degrees.

Also, the Euro modules need six-pin connectors rather than the USA four-pin type. The six-pin type are the same as the six pin connectors used for the tail lamp modules, so I bought them at the dealer, and it's easy to swap the terminal pins.

There's a photo of my car in the following thread:

http://www.peachparts.com/shopforum/tech-help/395876-odd-starting-issue-88-190e-2-6-a.html

Duke