I also replaced the tail light bulbs on my A-frame with 1157 LED replacements, bought at Walmart. My goal was to reduce the electrical load from the A-frame when towing and running the fridge on DC. Be forewarned that turn signal flashers don't always work correctly with LEDs because of too little current draw - mine had no problems, and I suspect newer vehicles have no issues.
On my A-frame, the tail light lens is removed by prying the side over a black plastic retaining tab. The clearance lights have bottom slots a small screw driver will fit in to pop the lens out. Very seldom are there screws; it's usually a tab retaining system of some kind. Study before prying.
2014 Rockwood A122 A-frame
2008 Hyundai Entourage minivan
camping Colorado and adjacent states one weekend at a time