C900 Headliner Repair
Before reinstalling the headliner, check the sunroof drains for blockage.
I use a garden hose and spray water in the sunroof box and make sure it flows down the drains.
Reinstall the headliner the same way it came out. Don't forget to run the dome light wire down the hole!
Push the headliner onto the A-pillars and then install the c-pillar covers to hold it up in the back.
Now replace the rest of the removed components.
The final step is to take the extra material around the sunroof and wrap it around the sunroof box and use the strip to hold it down.
Hopefully your hard work pays off for a couple years and doesn't fall down the next day!