Update...
Just cleaning out some old 'library' in the workshop. Came across a Kalmbach book, Toy Train Repair Made Easy, ca. 2000 by Ray Plummer. Among the several articles therein is one on the Automatic Merchandise Car No. 3454, page 46.
While not an official Lionel service document, it has some good tips for keeping it in operating condition.
Just thought I'd add to the thread subject...FWIW, of course.