I've got a Haynes manual here in front of me. It looks like most of the $1000 the mechanic wanted to charge me would have been for labor. You've got to remove a lot of things to access the belt. The actual belt replacement looks easy enough, though.
Just to clarify--if the gears slipped a notch, even without the belt breaking or slipping off, that would account for the car suddenly going dead while I was driving? Is that what you'd expect to happen?