My wife's birthday and Valintines day are the same. can anyone tell me how long I can store MMF so I can get a jump on doing 2 cakes on the same day ? 

feeln17, your wife and my twin sister and I seem to have a few things in common. 

Previous post on MMF storage:

http://cakecentral.com/t/752993/marshmallow-fondant

HTH

P.S.  Look forward to seeing pics of your Valentine's/Birthday creation.

Thanks! quess I can . At My age I need to start early or I'll forget what I'm doing (:

What is the best type of coloring to use to color  fondant? gels or liquid?   thanks!

I prefer Wiltons gel colors for MMF fondant. If you use something that has more water content, then just cut back on the water in your MMF recipe :)

at what point do u add, I've heard during the kneeding part if that is correct?

wrap the MMF in saran wrap and yo can make it 2-3 days ahead- I put the gel colors in when I am kneeding it, you can also put it in when you are mixing it together initially with the mixer. Remember that if you need Red to start with a pink or orange color and then to add the no-taste red--you don't need nearly as much doing it this way