You can do it by just taking off the housing cover. There is no reason to take the whole pump off. Get a new gasket too. There is only a shaft between the pump and the block. Make sure you mark the hoses so that you put them on right (if you take them off) and get the impeller turned in the right direction. Also, lube the impeller so that it doesn't stick the first time you start it. You can use dish soap.
Here is the cover:
Here is the impeller in the cover:
Here is the rest of the pump, you can see the shaft that sticks into the impeller on top and the shaft for the block on the bottom.