Doors come either plain or pre-hung, which work for different applications. With the Plain door, you have to do all the cutouts for the hinges and lockset. The pre-hung comes from the manufacture already pre-bored. If you are replacing an exiting door, you will need a Plain door. For a new opening, you will need a pre-hung door.
Installing a new front door can take any where between two to four hours depending on the weight and the amount of preparation some doors require.
Replacing your front door is not as difficult as you think; with a little elbow grease things should go smooth. Follow these directions to install your new door. The first thing to do before you buy a new door is to measure the old door and the door opening.
Measure the length (top to bottom) and the width (side to side), also measure the thickness of the old door and the way the door swing, left hand or right hand. Now you are ready to go door shopping.
Lay down the new door on a set of sawhorses.
Next remove the old door, wedge the door open at a 90º angle and use a screw-gun and un-screw the hinges from the jam.
Remove the locks, and hinges from the old door, then lay it on top of the new door, using the old door as a pattern, line-up both doors from the top edge and hinge side.
Use a pencil and mark out the hinges, doorknob, and cut them out. If the bottom needs cutting, cut that first.
Next place the door on its edge to chisel-out the hinge pockets. Reinstall the old hinges on the door.
Line up the new door in the opening and screw in the hinges to the jam. Check the fit by closing in the door, if the door rubs, mark the spot, and sand or plane it until it closes freely.
Install the locks on the new door, and new weather stripping.