plan on just the gasket and rear main. when you remove the pan, examine it and decide if you can reuse it or not. Just in case, order the new pan if the place accepts returns, that way you are prepared for the worst.
But I always save money that doesn't need to be spent, and if the oil pan is square, solid, and just a little crusty, I would simply clean it all up and repaint the outside of the pan and reuse it...that 56 bucks could go towards some nice fogs or a cool junkyard find...