[Keystoned]

I would not call it difficult, just time consuming. Like other repairs I have not done before, it starts out difficult and by the end it becomes easy. The last few feet along the top were the easiest and quickest.
The 2 dime size areas of wood I saw looked pristine. It was only because I removed dicor material that they were exposed. What was disappointing was that it appeared that there were several inches of gaps not sealed from day one that lead to eventual leaking.
Some previous owner noticed it and who knows who used silicone, which might have worked for a while. Either the guy I bought it from really didn't notice leaks or really lied about it. What comes around...
Anyway, thanks to all the advice offered here. I hope it is done with except for the rubber screw cover trim. I'll be looking for that today.