Are you 100% sure that the hinge pins are worn and allowing the door to sag? What you're proposing is a lot of work if it's not the cause of the sag.
I'd suggest getting a set of four hinges to practice on before you commit to working on yours.
Is it possible that the doors have slipped on the hinges themselves? They're held on with 6 bolts each side that you can access once the door card is removed. If the hinges aren't worn there is some easy adjustment here but it'll require another pair of hands to support the door whilst you tighten the hinge bolts. If you haven't got additional help then find a roof rack you can use by extending it over the side of the car with some box section, drop a length of studding through and put a hook on the end to hold the door in position whilst you tighten it up. A nut on the top will give you all the adjustment you need to get the door in the exact position. A pair of nuts below the box that you can lock off against each other will give you a datum point when you take the top nut off each time you need to check closing so you can carry on again.
If you've got the door off I'd also remove the screws holding the wing on so you can pull it away from the A post. I think there are three screws on the vertical face and on underneath. That'll give you a chance to better assess the state of the bottom of the A post. Corrosion here can lead to it's distortion and the door dropping.
