Not only does your old door look tired; the frame bows and the door will not close tight.
You need to replace it all – The door, frame, hinges, weather-stripping – the works.
Buying a door pre-hung in a frame will not only ensure a better ‘fit’. It will look much nicer.
A pre-hung door comes with a door in frame, weatherstripping, sill and hinges. And the bonus is you will be better prepared to install the door, level, plumb and square!
The door may be prepped for hardware. This means you are assured that that the Bore Hole and Cross Bore (hole between door and jamb) aligns.