So will the grain be more and more apparent the further I dilute the developer?
A little bit. Depending on the composition, you may or may not notice it. Grain structure is more dependent upon the film than the developer. All other variables being equal, the image with large areas of near continuous tone in the middle ranges will show more grain than an image with a more varied composition. and, as I wrote earlier, the differences don't really start to show up until you reach about 10x magnification. At that size, you'll be viewing the print froma further distance and the grain becomes less obvious.