You could chill the cake a bit before applying the fondant. I have never done this but I heard Duff say it last night on the show. That if the cake is a bit firm, it doesn't buckle under the weight of the fondant.
Then take a deep breath and do it! I find sometimes that when I just jump in and go for it, things work out better than if I obsess too much. (You should have seen the first time I put a dowel rod through a stacked cake, LOL!!) Good luck!
also, make sure you have enough to cover the whole cake and it might help to find center on the fondant and get that spot as close to the center of your cake as you can.
don't freak out and you will be fine. the more you think about what your doing the more you're going to worry. (at least that's how i am)
and like everyone else said, remember to breathe!
why are you nervous?? i looked at the other cakes you have done and they are covered in fondant...this one should be easy for you!!! you are a pro!!! Go for it!!!! you are a great fondant cover'er ahahhahahahaa!!! you know what i mean...keep us posted!!!!
It'll be fine, dear - put this in perspective! Remember, it's just a bit of sugar, flour and eggs... 
It's not Mission Impossible!
And if at first you don't succeed... well, you know the rest!
Quote by @%username% on %date%
%body%