I got my car back today, after having been without it all weekend. They said that their own dealer's service manual for my car was wrong, causing them to chase down a nonexistent fault in some part of the electrical system that required them to remove the entire dashboard. The problem turned out to be a faulty "system multiplexer" (whatever that is) that is easily swapped out in the driver's footwell.
The faulty part cost $130, and they spent FOUR HOURS of labor on that one little problem. Fortunately it was all covered under warranty, so it was on their dime. Phew.