I like a long needlenose pliers to grip the old impeller blades, one at a time, and tug away. The old impeller will come out easier than the new one will go in, because it's conformed to a memory shape. The new one will have to be introduced to that new shape.
Here's what the inside of the pump housing looks like. It's similar to the 4-port Sherwood we disassembled the other day, naturally by the same company it would look similar doing similar work. This one is a lot bigger and uses only one large impeller. The seperate cam piece of brass is placed on the bottom side of the photo, to work with the ports, to build water pressure and create the flow. These are replacable if necessary.
Regards, Paul
FXA 38 3004 R
Original 427 power