I know this is somewhat basic, but I had a bitch of a time trying to remove mine when I replaced my thermostat a year or so back.
I have a few questions on how to get the fan off.
What tool do most people use to grab the nut? All I had that fit was a large monkey wrench and it ended up bending and breaking some of the cooling fins on the fan. I ended up giving up on removing the fan and twisted the thermostat housing through the fan blades. It wasn't optimal.
Also, it seemed that the crank would just turn with the fan. I couldn't seem to get a nice impact on it. Looking back, maybe I should have put the car in gear?
(BTW, I know it is reverse threaded.)