Assuming its like any other outboard you should have two screws, upper and lower, fill from the bottom till it comes out the top. I always buy two of the tubes.
I have always used the little pump that you can get to screw onto the quart bottles. My outboards usually take a little less than a quart, but with a V6 I'd assume you have the "larger" gearcase. If I were you, I would get 2 quarts before you drain it, that way you won't run out halfway through the job. If you don't use it all, you'll be that much further for next year.
