Thanks for that, Eric.
I am starting to think that one is okay since I wasn't seeing two of the pins that were buried in hot glue on the board and tested incorrectly. I thought it was three pin, but it's five. Testing first and second pins now, Vin and Output, doesn't seem to short. The 37 volts is coming out of the silver PSU at the right in the second picture on the first post. I think that whole unit is fine.
Here's my guess (and I don't pretend to know what I'm doing with electronics, but...) - the board has to do two things - dim the light variably from the main voltage, and run the fan, which would run at a lower steady voltage. This LM2576 unit drops the voltage for the cooling fans, and the other mosfet, the 1018, is connected to the (potentiometer?) knob which dims the main light. I think that knob is fine because the digital readout still changes from 0-100%, just the light doesn't dim.
So I replace the shorted 1018, and bob's my uncle, the thing works again, right? Haha. Buying parts will let you know.