There's not too much use thinking about this really, I mean there's no confirmation that he doesn't know. Naruto might know that the 4th was his father and everything else but he might just not acknowledge them because of what he feels they did to him by sealing the kyuubi. I doubt he knows the full story behind his parents, but I think he has some inkling since he originally wanted to beat the 4th: http://onemanga.com/Naruto/1/13/
Obviously he might just have chosen him because Minato is considered the strongest ninja from Konoha in generations, but I don't think Naruto is that
Also, Naruto isn't that dumb. He was intelligent enough to pull pranks all the time as a child and get away with them. Most of the scorn he gets in the series is over his lack of knowledge rather than ability to understand.