To replace wood trim, remove the old trim with a putty knife and a pry bar, and prime and paint the new trim to match the existing trim. Cut the new trim to fit the door using a miter saw set to the appropriate angle, and nail the new trim into place using galvanized nails.
To remove the trim without damaging the underlying surface, cut the paint around the trim with a putty knife, and begin prying the trim off the wall at the bottom of the piece. Lift the trim carefully with a pry bar, and if the underlying surface begins to lift with the trim, insert a putty knife between the pry bar and the trim.
When cutting the trim to fit, use cuts that match the existing trim in the home, and check each piece to ensure it is perfectly cut before nailing it into place. To prevent the trim from cracking or splitting during the installation, predrill the nail holes.
To attach the trim to the door, partially nail the trim to the door jamb and wall. After checking to ensure the trim is properly placed, hammer the nails fully into place. The nails should extend into the studs and jamb by 3/4 inch.