My backup is (and has been) sad for a while, but I checked again and still I find no obvious vfd damage. So either the epoxied joint leaked and it lost anyway or there's a fuse out somewhere.

The question is, would it be smarter for me to just pay someone to fix it, or would the need to ship a spare vfd with it (I do have one) for potential replacement dictate that I should try more self-diagnosis (which I don't really have time to do at the moment)

There's only a few fuses, and they're really easy to check (assuming you have a multimeter).

Well, you said this was a spare. You can always try swapping the display modules between your spare and main empeg. As long as you do not plug the header in off by one pin (which will blow any fuses that remain), you should be able to see if the possibly broken VFD works in the main (suspect fuses on spare) or if the known working VFD still works in the spare (suspect VFD or display board).

I did swap displays, the main board is fine, i know it's the vfd or display board. I guess I left that out.

One more question - do you notice any sign of life from the heating filaments in the VFD? This might indicate if the VFD is receiving power or not.