You can get rid of the grain by killing the ambient light in the atmosphere tab. Set the light balance to around 60% sunlight, and ambient light from sky to around 60% too. You'll need a good measure of AA too, like min 9, max 12, set to optimized, quality 60% minimum, in the render tab. With these settings, you'll need to choose "user settings", no presets. I find all presets below "ultra" to be unsufficient, whereas ultra is too much. To print your render you'll need to render at 300 dpi, and choose the size yourself, depending on the size you want to print to. Expect very long render times!