Topic.

I wouldn't say its an absolute necessity that you need to play Crysis in order to understand Warhead but it wouldn't hurt to play Crysis anyway to get a feel for the plot and how the game works etc.

To get some of the stuff that happens in the game you'll have to have played Crysis since parts are intertwined.

You should play Crysis anyway because it's a great game.

The game is an expansion pack-ish, so yea you need to play the first to fully understand Warhead.

I'd say play at lest the first 3 hourse of them first crysis before you think about playing Warhead single player. You would not understand it at all.

There is no plot. Only teh graphix. If that's not good enough, we can't help you.