Yep you'll need a new fan viscous clutch. It is also reverse thread like you said. There are special tools out there but you can spend alot less money by buying a large strap wrench(SEARS,HD), wrap that around the viscous clutch and turn the nut on the water pump shaft the other way. I can't remember exactly what the size of that nut is...32mm? 34? Might also be the time to put in a new thermostat and have the radiator rodded out too, since you'll need it out of the truck to give you more room to work on the water pump(at least I did
).
