I have been fighting a cooling problem fro the past 4 months. It started with a leak at the pump. I read all the info here and bought one and the tool from NAPA. Also bought a thermostat and new belt. Got the cover off and removed the pump (right hand turn and a 18" breaker bar - very stuck). The cover bolts feel like 10mm but they are really Throx so the corners were broken some but it when back together ok. Didn't replace the cover gasket looked ok. Didn't replace the thermostat because they gave me the wrong one. Did replace the belt. Back on the road with new coolant and had a leak from the cover. Could only find the gasket from the dealer. Removed the cover and cleaned and honed (with 400 grit wet/dry sandpaper on a sanding block) and put back together (got new real 10mm bolts). More coolant and back on the road no leaks.
About 2 months later driving down the road chimes and all bad messages: engine hot, coolant hot, stop etc - limp mode home. Made it. Thought it was the thermostat at first until I noticed that the belt tensioner pulley had collapsed. The cheap plastic support ring for the pulley had melted. Dealer only sells assembly even though the pulley is removable ($100). Easy to replace. Back on the road. Then loosing coolant again. This time cap is not sealing and coolant venting to atmosphere. Replace cap back on the road. Drove about 1200miles and got check coolant level message. Sure enough coolant low about 2 quarts but system was under pressure so cap works. Now I think there must be a leak at one of the hoses or the reservoir. I am carrying extra coolant with me now.
So my advise to someone going for the water pump is do everything: pump and ring, cover gasket, thermostat, belt, belt tensioner and new 10mm cover bolts, and have plenty of coolant and tablets.