Are they the mayfair (Yellow colored)? if they are you don't even need a screwdriver there is a lever on the side you pull out slightly and push down then the cartridge comes right out - you twist it the direction indicated on the black lid and you will only need to cut the two wires (brown and black) and use an electrical connector to attach new wires.

Buy yourself a can of "LIQUID" electrical tape! coat your connectors! it's cheap.

If you don't have the mayfair replace your old ones with them they are awesome, I had both areator pumps go out and I used one of my two bilge pumps cartridges and put it in place of one of the bad ones and saved my sack of fish!!! I did it in 10 minutes or less while on the water!