STAGE 3: LOOSEN B PILLARS / REMOVE HEADLINER
Step 1. Remove lower B pillar
There are two pieces to the B pillar - the lower one has to mostly come out before you can get the top one out. Start with the lower door sills on the front and back seat. These are held in with clips, but using the plastic pry tool, you can lift away from the B pillar to expose the torx screws holding the lower B pillar to the frame. See pics of front (screw already removed) and back (screw still in) of the lower door sills below. Once these screws are out, there are a bunch of plastic and metal clips holding in the B pillar piece. CAUTION: this is where I broke the most clips, because the mount points are pretty far recessed into the hollow core, and it's hard to pry them out without good leverage.
Step 2. Loosen upper B pillar.
Once the lower B pillar is out, there are a few metal clips holding in the upper B pillar, and a plastic hook/tab locked into a slot in the ceiling. Pretty straightforward - pull straight out toward the center of the car, then tilt the bottom up to release the piece. BLOCKER: As far as I can tell, I can't remove the B pillar without removing the seatbelt mechanism. I'm not at the point where I want to mess with the safety equipment without knowing exactly what I'm doing, so for now, I'm just getting the B pillars out of the way to remove the headliner.
Step 3. Remove torx screws holding in the headliner in the center of the car (below the crossbeam). Prepare for hell.
Step 4. Start from the back of the car, and pull the headliner loose. In the very back section, there are five clips attached to the frame. These are the only clips as you remove the headliner - the rest is held in by some very tough "velcro" type fasteners. Picture below shows where the clips are (a couple stayed in the ceiling). All the black square are the velcro fasteners.
Step 5. Make your way to the front of the car, firmly pulling the velcro fasteners loose.
Step 6. At the front of the car, remove the mic panel (between the map lights) by pulling on the short side closest to the passenger cabin. This is held in by two metal spring clips, and hinges out when the clips are loose. Disconnect the two wires from the mic panel.
Step 7. At the very front, there are a few things now holding the headliner in (very hard to take pictures here). First, make sure the map lights have disconnected from the housings. Half of the housing (with the lens button) disconnects from the circuit board in two halves of a plastic case. Next, a bunch of wiring is taped/glued to the inside of the headliner, so start getting that loose. One of the wires goes to the rear map lights, so you'll have to follow that wire along the driver's side, around the rear, and back to the rear passenger side to get it loose. I put it into a coil and jammed it in the mic housing frame to keep it place while I was working. The last thing holding in the headliner is the friction fit between the ceiling, windshield, and rearview mirror plastic housing. It was really hard to see back here, but by jiggling around the housing on the rearview mirror (where it connects to the windshield), the housing loosened a bit and I was able to pull the headliner free, whereby it promptly fell on my head.
In this pic, the mic housing is on top (where I jammed the coiled map light wiring), and half of the map light boxes at the bottom of the pic. Remember the orientation of the plastic lens pieces in case they fall out - the cross shaped piece should be front and left on both lights in order to actuate the switch on the circuit board.
Here's another shot of the passenger side, where you can see how they attach the wire bundles to the headliner.
Once they're all loose, you just have a bunch of dangling wire bundles - I secured them to the ceiling using electrical tape.
Step 8. Pull the headliner out of the rear hatch.
This is the second most cringeworthy part of the process so far (the first being putting the newly painted headliner back in). Basically, you will need to turn, wiggle, and flex the headliner out of the rear hatch. Probably 100x easier if you have someone to help, but still, the size and awkward angles make it pretty tedious, and you will hear some noises that will make your heart drop. It's a pretty resilient piece and a lot of that noise came from things just rubbing against each other, but be careful and take your time.
Step 9. Relax, enjoy a beverage, and try not to think about the reverse process that's looming on the horizon.