So ... we realized we were overdue to have the grout in our shower redone, and we called a local contractor. The contractor came in, looked at it, and showed us that the wall itself was damaged. The wall itself had to be replaced, and of course they had to retile the whole bathroom (tile is a bear to match, it seems).
This kicked off in mid-January. Progress has been steady and professional, if slow and expensive.
Oscar, he who is easily startled, now calmly takes our contractors and the associated noise as routine.
Any project which goes on long enough for Oscar to accept as routine is too long.