I have my very old gold/silver guide here do you think its any use to me or should i just go get the new one...

I think the game is like 90% simular to the old ones maybe few new areas // persons

did they keep it so that you encounter different Pokemon if its day or night?

I would get the new one.

yes

i've already beaten the game on soul silver. i beat red. the game is different in a few places where i actually had to look it up. get the new one anyways. the pokemon also learn new moves. or you can just go online for a guide and pokendex n shit.

the game is different in very few areas, like on the island the safari zone was a cave.

i just use http://www.pokemon.marriland.com/

absolutely
better everything when you face it to the original silver/gold/crystal

And you can't catch Phanpy till a shit load later, it's pretty gay.