The assembly should pop out.
Nothing really to it. I'm not sure which side to pop it out on. The right side has metal clips, the left side has plastic arms that hold it into the headliner.
I would think you should pop it out from the right side. Mine I can just kind of grab it and pull and it comes out. And I can grab mine from either side, but the right side is usually easiest.
I had mine out today. The door behind the bulb has a little tab that can get broken easily. you only have to slightly move the flap release and pull up to get it open.
The bulb is the same one that the glove box uses. I took the one from my glove box until I can pick up a new one at the local parts store.
'92 300CE - Sold
2004 C240 - C7 Wheels
2015 ML350 - P1, Pano, Ash poplar wood, Sport Dinamica interior, Running Boards Keyless go.