Surfing around (maybe Google Images), an enthusiast had a complete restoration of the model you've mentioned (i.e. driver axles, motor, etc.).  In other words, it can be done, it has been done.   I'm sorry I can't direct you to his pages but it's out there.
Good Luck, learn a lot, have fun !!
PS -- I have the same model with the same plans ---- next year ?

Hello !
I've got this beauty apart except for the motor housing.  I can't find any identifying numbers but, from the looks of the PC board, assume the model is 10 yrs old.   It has the original "large" can motor.  I have the parts but want to test the motor before I go any further.   IF I touch the terminals of the motor directly from a DC power pack will I damage / burn out the motor ??
Thanks

I have several engines I'm investigating.  The one in question is the 4-6-0.  The previous owner seldom used it but removed the PC and converted it to DC.   Since posting, I've removed the motor and it seems weak.  Yes, it's a project but part of the hobby I enjoy.
Thanks for all your input.

Thank you, Gentlemen:
From your answers, I assume the development of Digital Command Control required the components of the PC board.
I've noticed some PC boards on newer products (engines), are smaller and less complicated.
When troubleshooting a poorly running engine, how do I know it's not the PC board ??

What is the purpose of the PCB board ?  My knowledge of electronics is limited to where the on/off switch is located and my experience takes us back to the '60's.