Whats the problem? You have a sagging door with a bad hinge bushing? You will need to get the proper hinge pin /bushing replacement kit. Comes with a new pins and 2 new bushings. To remove the door, you will DEFINITELY need 2 people, and then a soft blanket to set the door on so you don't scratch it. I'm pretty sure you just remove the bolts that hold the door to the hinge assembly. , but you'll have to support the door somehow as you remove the first bolt, as it's going to want to drop down a bit. Same with the last bolt. Again..... Get some help.. I've not done it before yet myself. Yet.
Oh I nearly forgot. If you have power windows / locks/ mirrors, you will have to unplug the wire harness inside the door and remove that rubber piece between the door and the car body. That rubber piece has the wiring inside and keeps them from getting damaged/ wet.