she looks pretty shitty indeed sir!
Is that brake fluid or grease i see in the pics?
Take the boot off and try lubing up the piston with some spray lubricant, and high temp grease, then apply the handbrake, wind it in, apply the handbrake, wind it in..... to try and get it moving first.....
with the boot off, you can see if the piston is pitted etc, and judge overall condition etc, before you go to the trouble of rebuilding....
It may just be clogged with shit that can be removed.......