Gary, assuming it is the same as the Midget, it is just a friction fit, you tap out the old ring by essentially turning about 1/8 to the left, you tap in the new one same way. That's the easy part.
Not sure how big 'B tanks are, but, one of my "to do" jobs on Ms Triss is to drop the tank and bend the arm on the sender as it touches the bottom of the tank too soon. This means the car is empty and 1/4 tank. Also, make sure everything is well grounded and this is a PITA to do twice.