Wow Baz, I could spend some time in that store.
Just so happens I'm working on a locomotive for my sis-in-law's husband who inherited it from his dad. I think his controller is toast and welded the motor solid. I've got a new one on the way.
I also fixed his daughter's loco which wasn't running right. Needed a new friction tire and track pickup. Works great now and will get a workout this weekend at the big family gathering.