Yes, I just learned that lesson as well. IMO a bit too ridiculously fragile.

I completed the firmware upgrade successfully. Then installed High Sierra successfully. Now my AirPort card is not recognized!

I had installed a AP card I had laying around from another Mac laptop (I think) that I had scrapped. So, I think that since the High Sierra software is assuming that this is a 2010 Mac Pro that it would also only have the AP card that came with the 2010 models.

My theory is that it will need a newer AP card than what I have. I’m honestly not sure what year my current AP card is from. Is anyone else having this problem or figured out a solution. If not, I will probably try ordering a newer AP card to stick in it or run an ethernet cable to it.