It's normal to leave the caliper in place.

The best technique is to force the pistons back into the bores with two screwdrivers.......one from either side.....so you don't jamb the pistons. This is done prior to removing the old pads.

After the old pads are removed, a wire brush should be used to thoroughly clean the cast iron slides where the pads ride. There are four surfaces on each side of the caliper for a total of eight. It takes a good 20 minutes to do this job properly.

Then, a very tiny amount of brake caliper grease (sold in packets at McParts) is put on each of the cleaned surfaces. The new pads will then slip right in and operate very smoothly.