I've been taking my car apart a bit at a time and last night I removed the interior header.
This is the part under the sun visors.
I first removed the interior light by taking a small screwdriver and prying on the small recess on the right side (switch side).
There's a push lever on the electrical connector to allow removal.
Move the visors out of the way and take the 2 screws out of their mounts and the single screw out of each of the visor clips.
There are 4 screws holding the header but now the mystery part.
If you pull the header toward you (back) by applying force at the windshield, it will pop down at the back edge easier. The front edge at the windshield has 4 hooks that go into the tridon so once the back is loose and down, you push the header forward to remove it. Now you can find the push lever on the seatbelt light, remove it and the header is free.