In re the PTC, if you're in no particular hurry you can get them for a dime a piece (free shipping from Asia) on eBay. Some suitable parts:
As GRJ says, the lighting board can take care of itself. The PTC protects the roller wiring independent of the LED lighting function. That is, a passenger car with stock incandescent bulbs and no "electronics" can benefit from a PTC to protect the roller wiring during a derailment short circuit. I think the logic goes something like: if you are going to open up the car anyway to convert to LED lighting, why not add the PTC. Otherwise, leave well enough alone.
