Before trying to remove boiler, did you verify handrail(s) are isolated from the boiler? Recall that the handrail(s) is the antenna.
Don't know about your articulated engine, I can only relate what I encountered when I removed the boiler of my 2-6-6-6 Allegheny Lionel 6-28028. The front articulated truck was attached to the boiler where the truck pivots - a post affixed to the truck has a slight bend at the top of it, bending toward the front of the engine. Starting at the truck going upward, there is a washer (hole in washer matches cross section profile of post), then a spring. After the screws holding the boiler were removed, I had to slide the boiler forward about 1/4" to disengage steam pipes from fixed truck to boiler, and then lift while moving the boiler forward a bit more to disengage from the post. Washer and spring came off post, but no problem putting them back. You might have enough clearance with your engine to look at where the articulated truck pivots and you might be able to see the washer and compressed spring.