It's mostly just pot metal, so not likely to be any good if it's that badly corroded. Also easy to break. The little lock bolt was the only steel piece I saw.
On the one I pulled out, there is a kind of bell-shaped cover that has to come off over the square output shaft first. The shaft is peened to retain the cover; I used the bench vise to hold the cover in a bit (against a spring) and the Dremel with a cutoff blade to grind away the peened area. With the cover off, there is a pin visible off to one side, which is what retains the lock cylinder. I tapped the pin out with a small punch (actually two of them, a very short one to start it moving and a longer one to finish) and pulled the cylinder out with the key.