No, the 3DS game doesn't look like it will be quite as dark. Like for instance there was actually a lot of blood (more subtle than over the top, which was a nice touch) in the original 64 release of OoT, and I'd be surprised if that was carried over to the 3DS release. I think it would be better to play the original material so you can be knowledgable about the changes and maybe appreciate the added detail more. 

I've played the game only last week for the 5th time in my life and I'm still planning on getting the 3DS version. I think it's a game that you will never get sick of, assuming you won't jump on the hater bandwagon.

EDIT: Sorry, I kind of misread. I thought you hadn't ever played OoT before. Still, I think it would be better to have a fresh reminder of the original.

I was in the same situation, until I bought Master Quest.

No one should deprive themselves of playing Ocarina of Time should they wish to.

That reminds me; I need to go home to my parents PRONTO and get my N64!

How much more added content is in Master Quest? I actually think the 3DS version will be built on Master Quest, not the original. MAkes adding extra content easier.

There's no added content. What this game do, is have different puzzles in the dungeons. I'm right now going to the Water Temple, and I can tell you that some puzzles are really good, specially the ones on the first three dungeons.