What special tool besides a water pump socket do I need to replace a water pump?

Thanks for the reply. Took it to a mechanic who told me that it isn't the water pump. Said it was two check valves that weep air bubbles from the cooling system. He said he called GMC and they told him that their was a Technical Bulletin out for the two valves. Is a technical bulletin anything like a recall? and how much should it cost to replace the two check valves?