I didn't try to drop the entire headliner. I don't have a moonroof, but I still think it isn't necessary.
All I dropped was the back and some of the driver's side. The back can be dropped by removing the two retainer pins. The pins are two piece. The colored portion that matches the headliner color can be pulled straight out leaving the black portion. The colored portion of the pin expands the stem of the black part. Once the colored part is removed, the black part can be pulled out and the rear of the headliner pulled down gently.
With that part down, you can find the rectangular hole in the roof brace where the light fixture lines up. The upper part of the fixture fits in here. Carefully measure to find a point on the headliner that is somewhere within that hole. Poke a hole in the headliner at that point. I used an edge of a razor blade but a knife would have also worked well. An X-acto knife would work very well. With the headliner fully pushed up to the ceiling so the hole in the roof brace can be used to define the limits, carve out the rest of the hole in the headliner. I used an old steak knife so I could saw away at it.
Then I removed the left rear grab bar from the ceiling and the B pillar molding (around the seat belt retractor). Also had to peel back the door opening gaskets. Next I removed the front dome light. Make sure you don't break the bezel. Remove the center part first and then remove the screws holding the bezel.
I had to use a fish tape (electricians tool) to feed the wiring from the rear to the front. I had the wiring from a Mystique to the rear. I cut off the portions I didn't need, and spliced the wires from the rear light to the wiring for the front near the connector to the switch.
Your experience may be different.