I wound up going a slightly different direction...
I'm installing a TCS Wow Sound decoder in place of the MRC decoder. Nothing was wrong with the MRC decoder other than its an MRC product.
I had a couple Richmind Controls LEDs hanging around. Having said that, here's the short version of what it takes to get the front end of one of these monsters apart. The compressors are the key. Pop them out and that releases the "front porch". Obviously, pull all the detail parts off such as the headlight and after coolers. Remove the lower portion of the steps that are ahead of and above the cylinders. The front cylinder exhaust line that's between the frame rails needs to be removed. It snaps in the frame of the front driver set. Once that's out of the way, the screw that holds the front cylinders in place can be removed. Be careful again. The valve gear has some little components that fit in between the frame and the front cylinder saddle. It's supposed to be the valve stems for the front piston valves. At this point, gently slide the wires through the opening in the boiler and slide the light and attachment forward. Remove the glue spots and take the light bulb out.
Assembly is the opposite of disassembly. In my case, I was careful not to pinch the wires for the LED when I put the screw back on that hold the front cylinders/saddle to the frame.
I've attached a couple of pictures. The first one is the light and the piece it is glued to. The second shows the Richmond Controls LED under the headlight. The third one shows the placement of the firebox flicker under the trailing truck...
If work cooperates, I should be able to test and set up the decoder Saturday morning.