Re: Water pump replacement
As Cat said, make sure you have a belt routing diagram. Then remove the belt to remove tension on all accessory drive components. Next, examine the belt. Note if it is cracked or shows signs of wear, especially on the sides (more on that later).
Next, check each accessory component for excessive play. The pulleys should not "wiggle". Don't forget the idler pulley. Spin the idler pulley to ensure it spins freely and does not squeak. Also spin the water pump. It shouldn't spin as freely as the idler pulley, but listen for noise and feel for roughness. Check the water pump weep hole for moisture. If water is leaking from the weep hole, replace the water pump. Pump replacement is straight-forward
If any other component shows signs of wear after testing, replace it. Same with the belt, and be particularly aware of pulley play if the belt shows signs of excessive side wear. Excessive wear will indicate a problem with one or more accessories. I replace idler pulleys about every 100,000 miles, just because.