That is one of GM's famous calipers with the parking brake actuator built in. You don't want to bother with the boot if the caliper is causing other problems. Replace the caliper. Years ago the special piston in them cost over $90.00 and the only way to bleed the air out of them was to fill them with brake fluid before installing them. If the boot has just been torn recently, once the caliper is removed, there's a wire wing to remove from the outer edge, then you pull the boot off the piston. If the boot has been torn or leaking for a while, the piston is likely going to have dirt caked on it or will have rust pits. With rust pits the piston must be replaced. Dirt can be cleaned off but either way the piston has to be removed. That's not a job for even an experienced do-it-yourselfer.
If you do tackle this, try to do it on the car without unbolting the rubber hose. Bleeding the air out should not be a problem but why take the chance on having a mushy brake pedal. Slide the boot and ring on just like the old parts came off. Once the caliper is reinstalled, you will need to operate the parking brake to adjust the piston out to the pads. Failure to do that can also result in a low pedal, and the piston will not self-adjust like all front calipers do.