They are LEDs to begin with from the factory and the resistors are there. Determine which wires connect to only the pickup shoe and ground from the axle mechanical reversing copper strip switch. Desoolder them from the shoe and the axle copper terminal. Follow the ESU terminal chart guide and solder the center stud power feed wire to the power feed terminal or wire on the decoder.
Then the ground wire or terminal on the decoder to the grounding wire from the led board on the coach. You can also splice in interior lighting and tail marker LEDs which include resistors. I've done that with Marklin LED kits and no decoder. If the decoder can be set to the same address as the locomotive, automatic fwd and reverse lights may work, but only with that locomotive. Otherwise, you will have to assign the decoder an address and toggle the fwd and reverse lights with the controller. Mfx and M4 decoders also work this way.
In order to dim the brightness inside the cab when driving in reverse, I used a thin piece of cardstock colored black and set it on the upper side of the led board