UPDATE: Everything has been resolved to my complete satisfaction.
I called the Galleria Apple Store today and spoke to the head of the tech department (who will be doing the actual work on my machine) and described the bad experience I had yesterday.
He apologized for the behavior of the Apple Genius (who had diagnosed all of the machine’s problems as being due to cigarette smoke before he even unpacked it out of the box) and said “Hey, you’re under warranty, plus you have AppleCare, don’t worry we’ll take care of you.”
It seems that I just had the bad luck yesterday of encountering a rabid anti-smoker.
Anyway, I’m expecting a call later today from the actual tech to tell me the status of my machine. After speaking with him, I feel better about any future dealings with that particular Apple Store; it was nice to be able to talk to someone who didn’t act like a condescending know-it-all.