Thanks very much for those details, guys!
I got one replaced on a GM 2500 van recently, by my mechanic friend as part of a waterpump job. Twenty one years old and 270 k km. He did an amazing thing in the first step. He noticed that the shroud around the radiator fan was in two parts, bolted together. It took maybe half an hour to get the upper half out but it really opened up the whole front of the engine. Then it only took a few seconds to take the belt off, bending the tightener with a wrench on its bolt. The tightener, an idler and the alternator had bearings that needed replacing. Changing the water pump was easy. I figure he saved me $500.