So back it went on Tuesday, with a much fuller explanation of the problem and me hanging out persistently saying I really thought it was a bad hard drive. A few tests later we had confirmation that it _was_ a bad drive. Which is a bummer, because I didn't have a backup. However, the Very Nice Man at the Apple Store sold me a La Cie Rugged 500 Gig external hard drive, which he proposed I do a backup onto. I had A. with me, so I pointed out that that just wasn't going to happen there at the store, as it would take an hour, optimistically, possibly much longer depending on how the drive decided to act. He made an exception and did the backup for me, replaced the hard drive and then restored the backup onto the new hard drive. All done by later that same day, altho I did not pick it up until today.
Despite me having a bad drive, and never ever ever having done a backup, I appear to have not lost any data whatsoever (you never know what you're going to find when you go looking), and it only cost me buying an external hard drive, which I would have had to buy had I been doing the backups all along anyway. Sure, it took four trips to Pheasant Lane, but T. got to ride on the little train on two of those trips, and I got to do some shopping on one of those trips -- not really a bad deal.
And that's why I Love Apple. Even when something quite awful happens, my never doing anything remotely resembling system administration doesn't particularly hurt. (Warranty covered the bad drive.)