Yes the door has to come off. Once you punch out the pins the hinge will be two separate pieces so you must support the door first. Shops have a jig contraption made especially for this, but you can rig something up and use a helper. Tape all the door edges and sills with something heavy like duct tape to prevent messing up the paint. Besides the pins you also need to replace the bushings in the hinge. All the parts come together in a kit from one of the restoration parts companies. You can unbolt the hinge from the door/body and rebuild it on a bench, but then you will have to realign the door upon installation. If your hinges are welded to the body and door (some are) then this is not an option.