finally managed to get a couple wires stuck to the pins of the decoder chip so I can tap it directly, and even managed to do it without cooking anything off with the iron in the process! YAY!
Project is nearing completion - I've got perfect operation.
Now I need to figure out a way to house it that's reasonably weather-tight (it's intended to be an "outdoors" thing), but doesn't involve spending any money. So far, the only cost has been time - all materials have come out of "The Pile". I'd *REALLY* like to keep it that way if I can figure out a way to make it happen.