I hope you take no notice of the nay-sayers, and just follow the good advice that some people are sending you. I made both my daughters' wedding cakes as a novice. Lots of practice cakes and decorating helped me, plus a good book from the library. These days you can get it all on youtube. The first cake was a traditional fruitcake, four tiers high, with almond paste and "plastic" icing. 3 artistic children aged 10,12 & 14 plus myself, made the hand-shaped icing roses of various sizes. The secondcakewasmoreambitious - German Chocolate Cake layers in the shape of a decorated hat. I think it haad 6 layers.The coconut topping was between each layer and "plastic" (can't remember the correct name) icing covered everything. Then tulle and flowers for the final decoration.It was beautiful. No dummy run for that cake,though.
So, go for it!