At the risk of answering my own question, I'm going to post these pics just in case any future questions arise.
The A-Pillar does not seem to be held in by any screws or bolts, but simply snaps into place. I used a trim removal tool to "gently" pry the upper part of the A-pillar towards the rear view mirror, NOT toward the back of the car. I say "gently," but it really took much more force than I was comfortable with! I agree with the above post that it was scary then the clips gave way, and I was convinced I had broken something. But fortunately, nothing is damaged.
Replacement is just a little finicky, and I had to press the forward part of the trim piece in first, then line the clips up as best I could. A firm whack with my palm seated the piece. No evidence of loosening or rattling, so far so good!
Pics provided to hopefully help clarify my messy description: