I'll join in agreement with a couple of other reviews here. Newhart is one of my favorite old programs, but this episode is not one of the best. The main thing wrong with it is that Dick is not consistent with his usual character.
The premise of the episode is not bad. Joanna was taken with the romantic ecstasy of she and Dick having a second wedding ceremony. Let's suppose hypothetically Dick had reacted to the idea civilly enough but in his usual rather deadpan manner, and had no particular opinion one way or other about any arrangement details. Let's suppose Joanna interpreted his behavior as apathy, or at least lack of enthusiasm. And he just couldn't convince her she was wrong to be upset. And every additional deadpan comment just got him deeper in trouble. That could be a good episode.
But as the episode actually stands, Dick goes beyond that and speaks rather thoughtlessly. Even rudely at times. The usual Dick can be a bit remote. But he's not a jerk. He's not a boor. I don't know what the writers were thinking. I don't know why the cast didn't speak up and say, "No, this isn't right. This isn't Dick."
There is running joke in this episode that the people who operate the greeting card store get invited to the wedding. Then we keep learning of one additional person after another who wants to attend because they hear about it from the card store people. That was the one part of the writing that showed some original flair. Too bad the rest of the writing couldn't be as good.