My worries about letting a drywall guy work on our plaster were for nothing. Phil is a miracle-worker. We'd spent the last 2 nights at my mom's, since Phil was going to be coming over so early (well, early for folks who work on 2nd shift! Plus, I ended up working a double shift, so I didn't go to bed until 6:30 am one morning). While we were gone, Phil taped up all the cracks and applied the first coat to the walls. He had cautioned us that the walls would still be wavy, and the corners might not be perfectly square. the walls I ddn't mind about, after all, they'd never been flat before! The corners had me a bit nervous, but I figured if I wasn't happy with them, I could always mess with them later.
Guess what we came home to? Walls that were flatter than I had ever hoped for, and nicely squared corners. He still has about 3 days of work left, but I'd be thrilled if this was the finished product, since it looks that nice. Well, except for the ceiling, which has just been taped and mudded in the damaged areas.
In the photos, you can see where Phil has filled in the "valleys" in the wall, since they are very light in color. The "peaks" are where you can still see the gray plaster through the mud. But it's all completely flat now...!