I think using Nintendo's version of the altered text would work best personally. Ganon has been referred to as a Prince of Darkness in multiple games to my knowledge, so it'd be best to keep that in.
Well, like I said, I'm not that fond of Nintendo's rewrite but I'm also aware of the shortcomings in my rewrite so I would love to see someone come up with something better as I'm not happy with it. And by that I don't mean hacking, a simple mockup will do. vince94's version reads much better than mine but it's too talky for my taste, and changes the color coding and font. Tomato's translation of the manual story for reference: http://legendsoflocalization.com/the-legend-of-zelda/manuals/
As far as I know, Ganon is only known as the "Prince of Darkness" in the original NES game, but I admit I'm mostly familiar with the classic games in the series so I could be wrong.
Zelda I manual: 大魔王 "Great Demon King", NoA translation - "Prince of Darkness"
English Zelda II manual: "King of Evil" (He's not referred to by title in the Japanese one)
Triforce of the Gods manual: 邪悪の王 "King of Evil"
In-game: 闇の魔王 "Demon King of Darkness", NoA Translation - "Evil King of Darkness"
The Dreaming Isle manual: 邪悪の王 "King of Evil"
Ocarina of Time: 大魔王 "Great Demon King", NoA Translation - "Great King of Evil"
Twilight Princess: 大魔王 "Great Demon King", NoA Translation - "Dark Lord"
At least for the early sequels, Nintendo of America consistently went with Evil King/King of Evil instead. I have no problem with calling him a Prince of Darkness, I think I came up with Dark Lord due to working within the space limitation. He's basically the satan of the Zelda universe and satan goes by many names, if not Dark Lord or Prince of Darkness, I could perhaps go with Evil King or Demon King?
Also wanted to say that I was playing the hack and I found a typo: The old man on the top right says "Show this to the old women." instead of "Show this to the old woman." I'm not sure if this was intentional; I'm PRETTY sure there's only one old woman in the game but I could be wrong.
Yes, it was intentional. Like Midna said, there are more than one old woman in the game.