I think this is where my rattle is, too.
How hard is it to get to that part of the headliner? I'm always a little nervous about removing my interior panels for fear of breaking clips and making things looser and rattle-ier.

It wasn't too hard, except that you have to remove all the plastic from the seats back to get to it. The clips won't break as long as you're careful and don't force them. Good luck!

Well, I worked on this area this morning, placing foam and duct tape along any wire under the headliner and running down by the side window, and I still have the rattles and buzzing.
I can't tell if it's just my frustration, but I think I may have made it worse.

Sorry to hear that.