Apparently, the rollers were badly corroded and the bracket that held the rollers at the bottom of the door was a complete wreck on each side from 20+ years of road salt and water. The cables needed to be adjusted too. The sum for the repair came to something annoying, but not unreasonable, so I told the fellow to go ahead.
It is *remarkable* how much more quietly the garage door closes now. As in, it used to sound like the house was about to come down and now you barely notice.
I guess it really needed some work...