Access to firebox flicker LED board

[billkohler]

I am converting a large-scale 3-truck Shay to battery R/C using a QSI Titan Magnum power/sound decoder.

This decoder has its own firebox flicker function which can drive the red and yellow LEDs seperately, just like the original Bachmann board does. However, the LEDs must be connected as common anode configuration, instead of the common cathode configuration that Bachmann provides.

I need to access the LED boards to reverse the LEDs. The ashpan board is easy to get to, but can anyone tell me the easiest way to get to the firebox LED board?

Thanks,
Bill Kohler