It’s not that difficult to replace a door in an old door jamb. Fitting a new door into an existing door jamb is a skill everyone should have. It does require some woodworking skills, but nothing that can’t be managed by anyone. Using the existing door frame is the simplest way to replace a door.
Fitting the Door
The first thing is to make sure that the door will fit properly when you replace the door. There should be a gap of about 1/8 inch all around the door to allow it to open and close easily and swing properly.
Where there’s not a great deal of wood to remove, you should use a wood plane. Always go from the edges of the door toward the middle and check frequently to be certain you don’t take off too much wood.
With a wood door, you should use brass hinges. This will give the best strength. Where the old hinges were, hold the door in the frame and mark where the new hinges will go with a pencil. Make sure the bottom of the door is supported so it’s off the floor.
With the drill, drill pilot holes for the hinge screws in the door. To affix the hinges, screw in the top and bottom screws of the top hinge, then the same on the lower hinge.