I have decided to tackle the board and try to disengage it from everything that's connected to it, so I can not only get at the diode, but take the opportunity to replace any remaining wonky components and check the traces, etc.
I don't have a video signal generator, so I'm going to have to rely on a conventional video source into the antenna input for now, but will try feeding into circuit in an alternate way, if I need to get to that point.
