In one way, I am glad your issue proved to be the less likely circumstance, because you had already procured the part and started to analyze the replacement technique. Proving it by substituting the unmounted regulator was the best of approaches because once hearing that one fire up, there could be no doubt in your mind you were on the right track.

And I learned something too. Never having done what you did, I now know it can be done. Thank you for following up with the story.
--
Art Benstein near Baltimore