Usually a master "stone-mason", specifically a "fixer-mason",
would be the primary skilled-craftsperson for your stone-fireplace & chimney construction.
You may also require a "master-carpenter" to cut/make openings for your fireplace & chimney
and structurally-reinforce those-openings.
A mason & carpenter could do the work themselves,
but often will also use apprentices, journeymen, laborers to do some the the work.