explorer 8.8 in an a-body: experience needed

The only retract action in a disc brake caliper is caused by a square ring instead of an O ring. If a rotor has enough runout to push a piston back into the caliper that rotor needs to be replaced.
There is a small amount of residual pressure in every antilock brake system. It isn't enough to heat parts, accerate lining wear, or cause any other ill effects.