The exhaust manifold flange where it attaches to the cylinder can be warped. This can and will cause premature gasket failure. When you have the pipe off lay a sheet of medium grit sandpaper on a known flat surface and rub the flange across the paper. You'll be able to see immediately if the flange is flat or has a warp to it. Most of the warpage I've seen is not bad enough that you can't sand it flat with a little time and elbow grease. The machined surface of the cylinder is usually pretty good but you can check it with the same method only use a flat file and sand cloth or paper to see if there are high or low spots that need attention. A good mating surface, a quality gasket and proper torquing of the fasteners will assure maximum life for the exhaust manifold gasket.
And no, you're not an idiot. An idiot wouldn't have asked for help.