So, now this is what it looks like. I had to go right down to the studs to make sure that I will get a good end result. My trusty dusty brother-in-law will be arriving next weekend to help me re-install green board.
I have only installed dry wall once about 25 years ago and I do not want to rely on my memory on how to tape and mud joints. If it was any other place other than the shower, I might actually try to do it without experience, but a shower is not the place to earn your stripes. Water damage is not fun.