one bolt holds the door handle on, two screws for the arm rest and an allen screw for the window crank then best to use a crows foot (trim tool) or two screw drivers may work and pop the clips from the door.
I believe I have found them and their covers($367). '75-'76 Darts, covers can be had from Year One at https://www.yearone.com/Product/1966-74-a-b-e-body/2fq75100u