I have a lavatory pop up drain that is in sink that is siliconed to the counter. The pop up tail piece goes into a trap adapter that is glued onto a piece of pvc into a drum trap. The idea is I can't remove the trap or drop the trap adapter to give some slack to remove the drain assembly. I am jammed between the sink and the trap adapter. How would you remove the pop up drain assembly and put a new one in without having to lift the sink off.

Thank You