A friend of mine replaced his standing rig at the dock, one wire at a time. He used StaLok or Norseman fittings (I forget which). I recall that he had built his own mast climber setup that functioned like the atn climber.
This was on a CT38. Big offshore performance cruiser.
So it reallly depends on your knowledge and skill level. Me - I'd hire a rigger! (And did so for our new rig.)