You have to make a tool that will slide between the shafts and the nylon retainer in the seat back. There is a notch around each of the shafts, which engages a tang on the retainer. You push the tool between the shaft, and retainer keeping the tang from engaging. They show a picture in the FSM, but no dimensions.
Was looking for the same thread also. Put some seats in my cousin's car last nite minus the headrest. I just un-hooked the seat cover and pulled it up far enough till I saw were the headrest poles were locked in. Took a flat head screwdriver and held back the plastic tab and pulled them right out. Pulled the seat cover back down and re-hooked it.