This set is not as simple as you think, and way beyond the repair of probably 95% of those that do repair on Postwar trains. The mechanical side could be managed without problems, by refreshing ALL capacitors, put in new resistors, and add a new tube. That's the easy part.
The E.C.U. transformer has 10 pushbuttons, that perform different functions, for uncoupling, whistle control of tender, and unloading the dump car. The E.C.U. is actually a RF transmitter, and operates on frequencies from 240khz to 360khz, and then you have 5 different receivers, 3 which are low frequency and 2 high frequency. Each receiver does certain functions, and are designed for specific cars within this set. The receivers are (low freq.- RUA1, RU1, RUD1); (high freq.-RUC1, & RUB1). There is a complicated process in tuning both the E.C.U. to transmit specific frequencies, and then tuning of the individual receivers. Unless you have a pretty good, no make that a very good to excellent electronics background, plus having a Signal Generator, and other various pieces of test equipment, bringing one back to life is no easy task.
I would put repairing this old set, at age 69-70 years old, way beyond the scope of the bulk of the forum members who do repair. It takes more than replacing parts, and a workbench with the right equipment to fix it. Granted this set was actually ahead of its time, when offered, but is archaic by today's standards with the newest offerings. It would take to much time, money, and equipment to fix it to running condition. One major thing that is stated is the track must *repeat* must be immaculately clean. Consider it a "Shelf Queen" and just display it.