Nissan uses plastic trees to hold the panel on. I suggest an interior popper tool to get them out or else you will ruin the particle board panel the door trim is made with. Use some kind of hook to get the retainer out from inside the window crank handle. also remove two screws holding the arm rest/handle.

Heath

There's also a couple screws on the armrest that need to come out, and the same tool can be used to pop the little wire clip on window cranks if you don't have power windoes.

I call them "jesus clips". Usually when you pop them off the window crank, they go flying and you shout out, "Jesus!", among other things.