First class on NW is nothing special... bigger seat and you'll probably get a meal of some sort... for me, I wouldn't pay to upgrade.. I'd just try to get the coachchoice exit row seat to get out of the middle seat and be happy with that. Haven't got a clue what the cost would be... I can tell you a co-worker of mine was recently offered an e-first upgrade on MEM-MKE and it was $50.