Alien Bees Fan replacement instructions?

I bought a couple older AB800's, and they work great but have the old style noisy bearing fans that I need to replace. One is especially bad, rattling and groaning. How do you get the main board out of the unit to get to the fan? I have the tubes and main plate off, but don't want to just pull on the board, it seems pretty snug. AB want's $80 to do it including shipping, I don't want to pay that for a couple $5 fans and 15 min time.

Thanks!
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