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It's not hard to do. The best way is with a fan clutch wrench set. This will have a spanner wrench with pins that will engage into the holes in the water pump pulley, and another large wrench to turn the nut on the fan clutch. You should be able to pick one of these up at a tool store like Sears, or you may be able to rent one at a parts store.
You can also try to hold the water pump pulley with a screwdriver or prybar, driving it in behind the pulley. This isn't a great idea though if you aren't replacing the water pump because it can bend the pulley.
Once you get the fan off the engine all you have to do to remove the clutch from the blade is remove the 4 13mm bolts and seperate the two.
This is what holds the pulley.
Here is the wrench. it's the same size as many Fords.