Making My First Cake --PLEASE HELP!!

Good Morning Everyone!

I am making my very first cake using fondant and gumpaste. So far I am having a blast playing and learning!
Here's my problem:
My family is having a B-day dinner on Sunday night and I am making the cake. I am leaving Fridat night for a girls weekend (which I am VERY excited about, no kiddies for two nights lol) so I need to have the cake done before I leave as I wont be back till late Sunday. My plan was to make my Mud Cake today (Thursday), fill it with white chocolate ganache, fondant and decorations Friday.

1) Can I leave the cake out on the counter covered in fondant till Sunday? Will the ganache be alright left out??

2) Does the cake have to go in the fridge? Will that ruin the fondant and gumpaste decorations?

3) If I can't use the ganache, which my heart is really set on, what goes well as a filling for a Mud Cake that can sit out for two days?

4) Do I need to cover the cake with seran while on the counter or will the fondant act as a sealant?

Thank-you so much in for any and all help I really appreciate it!

Victoria