Fuel leak from top of tank, passenger side
 

Hey folks. I'm experiencing a fuel leak. It has run down from the top of the tank on the passenger side. It only happens when the tank is full. I looked around and found the gasket for the fuel gauge bobber is "damaged"(see photo). Could this account for my leak? How could this have occurred if the unit has never been removed? I've had the car for 3 years and it only started about last September, it has been parked in the garage since November.

What is the "proper" way to install this gasket without damaging it like this one?
https://uploads.tapatalk-cdn.com/201...f0e45d272a.jpg