Reply To: How hard is it to fix this?

Success!

Steps for the really bad window:

1. Clear Custom Split Normals Data. See ugly shading square.
2. In Edit Mode, delete two apparently unnecessary overlapping faces (thankfully no holes appeared) and move one vertex with GG slide. Observe ugly shading almost eliminated.
3. In Object mode, shade the PrimaryHull flat. See ugly shading disappear. See undesired subtle creases in the hull.
4. Shade the hull Auto Smooth. See ugly shading again at the default 30 degrees.
5. Set the max angle to 10 degrees. See both creases and ugly shading disappear.
6. Check the two not-so-bad windows in the top right. See that all ugly shading has disappeared.
7. Go make yourself a nice cappuccino and bask in a job well done. So far. 😎