Replacing a front door lock is a relatively simple task that can be completed in a few steps. First, you'll need to slide the new lock and faceplate into place. If the new faceplate doesn't fit in the slot on the old faceplate, you'll need to hold the new face in place and trace around it with a pencil. Then, use a chisel to carefully remove any excess material until the new faceplate fits.
Finally, screw the front plate to the door. Be sure not to overtighten the screw if you use a drill. The entire process should take no more than an hour, depending on your skill level and the type of lock you're replacing.