While tracing wires to troubleshoot a high-mount stop lamp issue, My A-piller trim pried out with encouragement from plastic trim tools - the service manual has a good view of where and how the clips / locking features are located and oriented. Wearing gloves helped prevent smudging the 'mouse-fur' on the visible side of the trim. Tackling this on a warmer day / in a warm workshop helps prevent snapping of plastic bits injection molded during the Bush administration...