do i need a brake flush with a caliper and brake pad replacement (it was sticking, pads down to 1mm)
Yes on the brake fluid. Brake fluid absorbs water that is why it is recommended to be changed every three year.
Unless the mechanics find something wrong with the calipers there is no reason to change them.
The rotors are another matter. They will have to be measured to determine if they can be turned or require replacement.
You are past due for brake fluid replacement and if your pads were that worn you most likely have rotor warp or damage. Just have it all done at once and you are good for years.