Snowed here today, trapped at home, thought I would putter around on my 1990 190e, since I didn't have a working rear dome light and the garage was warm. I couldn't get the lens off, did a search under dome light, came up with the little trick of a small blade screwdriver inserted into slot on passenger side of lens, the whole thing came out, great, all one piece, raised the metal flap to expose the bulb, it looked ok but where were the wires???, checked the housing, no wires??? With my trusty flashlite I peeked back into the right side of the housing, there it was, had somehow pulled itself off the prongs and recessed itself behind the headliner. Well, this job calls for my trusty long nosed pliers, it came painfully and slowly from its nest, a little tight untill it came clear, plugged it in and there was light, worked the door buttons, all OK, tried switch on the dash, all OK.  Thanks to Tech Help and the Forum, I was able get this apart.