Answer - Internal
door handles can take a lot of wear and tear but it's a simple job to change them; all you need is a screwdriver.
Remove the old doorknob, the latch, and the strike.
You will need to know the back set; this is a distance from the edge of the door to the center of the hall. The rear set on the door must be the same as the lock, although some are adjustable.
Put the latch in the hole and tighten the two screws making sure the bevelled side faces the door jamb.
Install the outside lever and then the spindle through the latch.
Install the inside lever and tighten the screws until the lock is firm.
Match the screw holes on strike with the centre lines on the door jamb. Test that it works smoothly.