Trading over Pokemon to B/W?

[i_heart_cameron]

Hey guys, I was reading up on B/W and I read you have to get the National Dex AND beat the game before you can trade over any Pokemon. Is that true? If so, how do you get the National Dex?

Would it be possible to use an Action Replay to put an older Pokemon in the game? This may be weird but I don't think I'll enjoy the game to the fullest without my fave Pokemon SNEASEL.

Thanks guys!