There are many steps to replacing a front door. Here is a brief synopsis:
1. Get an accurate measurement of the existing opening. This can get tricky because there are several factors to consider. Making sure you get it right is key to making this project work.
2. Take off the trim, trying to salvage as much as you can as you may need it. Secondly, take out the hinge pins and unscrew the other half of the hinges. Remove the door, sill, jamb and door frame.
3. Check the waterproofing and flashing. Most likely you will want to replace this.
4. Next you will need to set the sill. Use a level to make sure the plate is even.
5. Apply caulk and install the frame. Check that the frame is plumb and square, using shims as necessary.
6. Nail the frame and hang the door.
7. You will need to use a minimally expanding foam and caulk for insulation between the jamb and the frame.
8. Add the interior casing and hardware.
Finish up – if your new door is raw, you will need to apply a sealer.