It seems to me that you have to use finger pressure to press in the left shell latch to allow the action bars to slide free from the receiver. This is also true for reassembly.
Yes, i thought of that after i posted, just figured at that point,
he would have seen what was preventing the assembly from sliding forward.
Simple push with index finger and out she goes.
1. Take pliers.
2. Insert them into the fore-end tube.
3. Open up pliers so they are tight against the tube's walls.
4. While holding the forestock firmly, unscrew the fore-end tube until it slides out.
5. Replace with new fore-end stock.