Thanks, Thymeclock . . It was bad news.
I just got off the phone with Chevy, and coincidentally, the 5yr/100K warranty expired 2 mos ago.
My mechanic's quote is ~$3,000.
Bear in mind that the Aveo is an '09 w/72k easy miles. I've had a few cars myself, and that's the shortest lifespan I've experienced.
I'm going to donate this disappointment, forever close the "Buy American" chapter of my car ownership experience, and buy a brand new Honda Fit for $15k (what I should have done in the first place).
Living Stingy: Should You Buy An American Car? Probably Not.
FWIW, My rental has been driving a Toyota Yaris, which makes parting with the Aveo that much easier.