We just changed our on our 1996 Dodge Ram 1500. It was a bear until we finally got the right tools to do it with. We needed a 36mm open end wrench on the fan nut (between the fan and the water pump. We had to take off the drive belt to get to the water pump cylinder (wheel) which we had to use a large belt wrench on to hold it in place in order to loosen the fan nut. Once we did that it was just a matter of taking out the bolts that hold the water pump on. Make sure to have a large and wide bucket below the engine to catch the radiator fluid that will pour out as you take the various hoses off that are attached to the waterpump.
Have fun. It wasn't so bad after we figured out which two wrenches we had to use.