This is just a FYI. There is a fellow, Benjamin, of BenzTrainz, on youtube that has lots and lots of posts about repairing O gauge trains. He specializes in old, used, and mostly broken Marx trains, but his fixes, repairs, and hints are universal for all O gauge trains. This guy is the Mr. Wizard of toy trains in my opinion. We have all found ways to fix things when parts are not readily available, but Ben has taken repairs to a new level, by using ideas and parts that cost next to nothing.
I think he deserves a look. You may find some of his ideas interesting, and perhaps actually useful.