My advice is to install a rebuilt caliper with a brand that matches the other side.

A stuck piston, in my experience (even if you can free it up) means that it will always be prone to re-sticking. Once it corrodes to that point, it's toast.

__________________
1981 300TD 310k miles
1970 280sel 172k miles
1966 230 Fintail 162k miles

"Where are we going? And why am I in this hand basket?"