RPB

I own a 95' C-Class, I replaced the rear dome light bulb and now none of my interior lights work, if I move the dome light around the metal surrounding the lights will flicker. My housing has 4 prongs sticking out of it, but only two of them plug in. This light must be the ground for the interior lights. Can someone please shed some light on what is going on please? I do not want to cave in and pay those ridiculous labor rates at the dealership. I need my lights back, I would really appreciate your guys expertise!!

Thanks.