mth locomotives are for the most part easy to work on. lionel is another story. I just fixed my lionel legacy mikado smoke unit and what a piece of junk that smoke unit design was. trouble with being a tech it seams is every time you get a new engine to repair they have changed the electronics package. legacy, lionchief, lc+, lc2.0 and so on. since mike gave those classes I bet the electronic pakages have changed a lot. especially now that blue tooth is invoved.
so just like cars now a days its becoming a more and more specialized job. not to mention some things are just poorly engineered by especially lionel which makes working on them even more frustrating at times. I am sure that working for say lionel as a hourly tech does not pay what its worth either. hope you get your coal load working again. I am sure you will.