Calipers are most of the time just fine.
Squeeze it all the way in. Then change brake fluid. That helps a lot.
But the most important part is to clean the sliders/pins. They have a great tendency to get stuck.
If you manage to get them out, clean, wipe old grease, apply a tiny bit of fresh one, and put together with new bushings.
I never had caliper stuck, but had many pins rusted and stuck.
I had the brakes and rotors installed today. The rear brake pad holders were rusty and did not operate freely. A couple of the front pad were worn, but the front rotors were still in pretty good shape. No work was needed on the calipers. I'm glad I had this done. Thanks to all who posted!