Star by getting a oil pan or something to catch the coolant that will leak out. With the belt still on, loosen the 4 bolts that hold on the pulley. Then remove the belt. Remove the 4 bolts from pulley. Then there are 4 or 5 bolts around the water pump, remove them. The pump will be hard to squeeze out of there but it can be done. Clean the old gasket from the block. Make shure that none of it goes into the engine (it could clogg the radiater). Use a new gasket and revese these steps. Rember to use LOCK TIGHT on the 4 pulley bolts or the pulley will work itself loose. Its best to change the belt at the same time too. And to a radiater flush also. Happy Corsica.