I don't think it was a PITA, say, compared to dropping the Tcase Admittedly, I practiced in the junk yard when I pulled the sunroof cassette so I was more confident and took a lot of pics.

One of the biggest thing to dropping the headliner is not to break it. I mean you can bend it but don't want to put a huge crease on it. I tied straps and rope around the whole roof/ceiling to support the headliner and to support the sunroof cassette during removal and installation. The headliner can't be easily removed from the vehicle due to the wiring harness that goes to the second row dome light and the entertainment system console gizmo. This harness is glued to the backside of the headliner. Nice going Toyota!

There are four color matched plastic clips toward the middle and rear of the ceiling that should be popped out using a trim removing tool. This is the tool with a Y at the end of it. I used a piece of 1/16" alum plate to pry this tool against as I didn't want to dimple the headliner.

Toyota is using velcro around the perimeter of the sunroof opening to keep the headliner attached to the sunroof cassette.

Here's a pic of the headliner, harness and a mouse nest!
Shared album - A. Ali - Google Photos

Here's a pic of the sunroof cassette being supported by the straps
Shared album - A. Ali - Google Photos