I did my daughter's wedding cake - never done one before, though i bake a lot. Searching many websites i ended up being recommended the Cake Bible by many people, and indeed it was the most useful of all. I highly recommend you buy it. She explains every detail of the baking (esp the differences in baking a very large cake - like 12 inch diameter) and how the recipe has to change, she has wonderful recipes, and also the structural construction aspects.
I made, on my daughter's request, a fudge cake with dark chocolate raspberry ganache, filling and white chocolate cream cheese butter cream as a crumb coat (under the fondant) - a fondant frosting. I did it in 100 degree heat without air conditioning, freezing layers as i made them, constructing it at the last minute and transporting it to the wedding place in a huge box, where they had a fridge.
It was 6 layers, three tiers.
Her description is very good and you can't go wrong. Make a small version to try first. She also has a website and you can ask questions and she'll answer (I did and she did).
For anyone interested, this was how the cake turned out. The bottom tier was a very dense and moist banana cake with caramel filling, the middle tier was a lemon cream cheese pound cake with a lemon curd and fresh blueberry filling, and the top tier was a dark chocolate cake with black raspberry mousse filling. I also made a chocolate stout cake, a peanut butter cake, and a fresh ginger cake which were in the kitchen for slicing and serving efficiency. All were frosted with white chocolate buttercream.