Please do this at your own risk. I am not responsible if you break anything. End legal mumbo jumbo.
Okay, so I am redoing almost my entire interior so expect a few more write-ups.
Also, this is done on a 1993 318is, other E36's, ecspecially newer ones, might be differemt.
If your headliner is saggy and falling down like this:
It is time to replace your headliner. In this DIY, I will cover A,B and C pillar removal along with back dash removal, rear side panel removal, and side bolster removal.
This is not hard, it is just an undertaking and it takes time. I did this (with frequent breaks) in about 1-2 hours.
To make it easier to move about the cramped car and to get the headliner itself out, I removed the front passenger seat. That is easy, just remove the four bolts that hold it to the floor and lift up, not forgetting to unplug any wiring harnesses from underneath:
Now with the removal. The headliner is held in by everything below it. A,B and C pillars, "oh shit" handles, sunvisors, you name it. I began this removal with the sunvisors.
First, unscrew the sunvisor clip, then unscrew the sunvisor post and disconnect the wiring harnesses from both. Then to remove the light, simply wedge a fingernail under the part that is closest to the front window and pull back. Unplug that wiring harness too.
Here you see the front of the car sans sunvisor.