Hi, There are 6 screws. 2 right up the front on the clear plastic. 2 by the side of the water tank, remove the tank is easiest, and 2 at the back of the machine. You also have to unscrew the clear plastic top of the flow meter. The pump itself has 4 screws that are easy to see.
Why do you need to replace the pump. If its the 1698 series and it sprays when set to accessories but not when set to floor it will be the heater box, behind the red light on the handle base, water channels that are gunged up.
I took mine apart, cleaned it and it works fine. Don't mess with the pump. It's sealed and you could damage it.