I just changed the oil and replaced the water pump and now it will not start.

I would have to suspect a wiring connection got disturbed (maybe a brittle wiring harness just decided to die!) during the water pump installation. Is the crankshaft position sensor or camshaft position sensor or harness anywhere near the water pump? Could a vacuum hose got knocked off. An engine needs mechanical integrity, spark and fuel to start. Do you have spark and fuel pressure? Autozone have some popular workshop manuals for free on line once you register (for free) on their website http://bit.ly/autozone_repair_info. There is a company that independent auto repair shops get their information from, this same information is available inexpensively for people that work on their own cars.. The information is year make and model specific, covering repair procedures, torque specifications, fluid capacities and specifications, service bulletins, component locations, wiring diagrams ect.... Alldata is very easy to navigate http://bit.ly/AllData_Repair_Manuals_Online

if your timing belt runs with your water pump the marks could have moved