You don't need to remove the caliper to change front pads. Just remove the bottom bolt, lift up the caliper and tie it with a piece of string while you swap pads. Be careful that the antirattle springs seat properly as you reinstall the caliper.

To retract the piston attach a bleed hose, open the bleed valve, support the back of the caliper against something solid with a wood block and use a hammer handle to push the piston back.

On each rear caliper, attach a bleed hose, open the valve, remove one pad, push back the piston, install the new pad, then do the other pad.

I assume you want to flush the system. After all other work is done siphon as much from the reservoir as possible. The rear is tough to siphon because of the baffling, so bleed it nearly dry. Carefully watch the inside rear of the reservoir to watch the level. When it's almost empty, fill the res. with fresh fluid. Rock the res. back and forth and be sure the rear res. fills.

Since the rear res. is tough to see, many think the res. if "full" and start bleeding, then can't understand why all they get is air and there is no pedal.

Duke