Backflush the cooling system thoroughly and change the thermostat while you have it apart. The previous pump impeller may have exploded, and leftover pieces can cause early failure of new pumps. If the heater core or bypass line are partially clogged, the pump will experience raised head pressure which can cause the seal to leak. I have had this happen, and one guy had something like five pumps in less than two years.
Do yourself a favor and take out the air filter, intake duct, and battery for plenty of room. Gasket normally comes with pump.
