If you turn the volute over, you will be able to see the metal seat of the shaft seal. Using the 1 1/4" pvc pipe (or other material with the same diameter) and hammer, lightly hammer out the shaft seal. Make certain that you are not hammering the surrounding volute housing otherwise the volute will need to be replaced.
Once the shaft seal has been removed from the volute, you can use the flat head screw diver to remove the other half of the seal from the impeller. Insert the tip of the screw driver in between the rubber boot and the body of the impeller and gently push down towards you. This should lift the shaft seal enough so that it is easily removed by hand.
Carefully lift the shaft seal and place it into the volute. To install the new shaft seal properly, you will need to use the 1 1/4" pvc pipe or a 1.5" male threaded adapter. The pipe should fit over the spring portion of the shaft seal. Using the pvc will allow you to hammer the seal into place without damaging it in the process.
Your booster pump repair is now complete. You can reconnect the hoses and turn the power back on. Let the pump run for a few minutes while inspecting for leaks. If there are no leaks present, job well done. If there are leaks present, turn the power off to the booster pump to repair the leaks.