How to change the pump motor thats inside of the fuel pump on a98 land rover discovery?

i have the pump out but there's a black sack on bottom ,how do you take that off How to change the pump motor thats inside of the fuel pump on a98 land rover discovery?Fuel pump is one unit- replace that unit. By the way, if I recall correctly, this truck is due for a fuel tank recall. If it is, and the fuel lines break upon removal of the tank, they will replace the lines and the pump, at least they did that on my '96.