So yeah... I am not into warhammer, so is this a stand alone game? Or part of warhammer, with all the existing warhammer units?

Errh.. Its standalone board game set in the fiction of the warhammer 40,000 universe; As such it does not require you to own any other warhammer miniatures, rules books, etc.

You actually don't need to know anything about the Warhammer lore either: in that case, you'd see it just as a heavy-on-strategy sci-fi boardgame!