There are methods to keep new air from getting into the system when swapping a caliper (pretty easy with your single-line ABS calipers) but unless you are sure all the fluid has been flushed in in the last couple of years, it is time well spent to bleed each until the fluid looks like Bass Ale instead of Guinness Stout.

Just warning, if you use the pump, pump, hold method instead of a pressure or vac bleeder you need to avoid running the pedal through more travel than is used in normal braking. Put a block under it.