A Group Puzzle of Extreme Difficulty

Well in 2 days I'm going to be leaving for 2 months with very limited internet access so here is a little goodbye gift for everyone on S.G.

Ok to keep it short and simple this is a group puzzle so everyone is allowed to talk about it. You have 3 weeks to crack my clever code and get to the giveaway. You will be given no hints as of now except that it has to do with the alphabet backwards and ordered pairs. So all puzzlers put your heads together to solve this one. I will give a sample text.

Encoded:

NHZMHKCLWOCZNNKCLCZLCKCNMKCNMKCRN

Decoded: I HAVE 10 BANANAS

So to get to the giveaway decode:

MCOMNMLHMRKCORKWLMKCORNHOMNMNRZOMNMZMCOMMKRMLMOCORNHNMLHZORMHOCZKRKWZZZZLMOCZORMHOCZLHNHLWOCKMCWKCOWZMCOMNCOCZNHNRZLCMRLCMCNNMHZOCNMOHOMOW

http://www.steamgifts.com/giveaway/XxxXX/ and a capital X can be a number or letter.

Special thanks to Yatterman for helping me out with everything. Think off the grid and best of luck to all!