The only electrolytics I've seen that degraded in model train electronics has been the ones on the old MTH 5V boards. My suspicion is those are the early 2000-2002 batch that was defective from the factory and were widely reported about in the capacitor plague.
The most common issue I find is some oxidation of contacts on connectors and the PLCC RailSounds chips. Neither is difficult to address, and I have no problem buying used stuff.