If it’s dry sand, always rinse it.
Adding it slowly is the best way to do about everything in this hobby, but I’ve seen people change a whole 8” cylinder of calcium reactor media (including myself) w/o much issues. It will stop growth for a bit and nutrients become less stable, but after it settles in it’s good to go.
One time I removed an entire sandbed via siphoning in one day w/o much issues. There was obviously a destabilizing event, but nothing died.