water in gas tank

My kid dumped a jug of water into the gas tank thinking it was gas. I disconnected the fuel filler hose and used the opening on the tank to
pump  everything out where the last gallon was 90% water & about 10% gas.
Since I've never done this before, what's a good way to proceed?
Should I replace the fuel filter? What does water do to a fuel filter?
Now that the fuel tank is completely dry, should I run the engine with the
water that must still be in the lines?
Should I run only one gallon at first - and then when empty, add the rest
of the 18 gallons?
How do you approach this situation after pumping the fuel tank dry?