

Adding doorframe & door
I would like to add a door at the start/end of this hallway. I haven’t been able to find the right contractor so thinking about doing it myself. My question is - I’m sure the right way would include cutting back all the drywall and then framing in, but what would be the downside to just installing framing on top of the drywall? The upside of that would be that while I would have to even out the walls with strips of drywall they would be hidden by the door molding and I would not need to mud or paint.
The existing opening is 86x42.5 inches. And I want it narrowed to 82x38 inches for a standard 36 inch door.