2000 Acura TL changing a ceased rear Caliber

I assume you mean the rear caliper.

First of all, did you try to push it back into the caliper? Or did you twist it back in? Because those calipers are not like the front calipers that just push back in. They need to be pushed it.

If it is still seized, then since you already have the caliper off from the anchor all you need to do is unbolt the flex hose from it and possibly the parking brake cable if it does not have parking brake shoes.

But first make sure that it is seized before you replace it. Alot of people think the rear pistons just push back in, when infact they do not.