I always put some red RTV on that O-ring. No gasket, as it will space the O-ring too far away for a good seal. Been working on vehicles since I was 8, so when you get to tightening that pan gasket (cork) watch the edge of the gasket as you are snugging the bolts down and when the gasket JUST starts to bulge out a Little, THAT'S TIGHT, go no further and you will have no leaks. You're on the right track with being detailed.