Here is what i do. I cream my sugar and butter/marge for a good 10 minutes, then i add all the other ingredients at once and mix for about 3 or 4 minutes. Then i cook on 150 for about an hour. I let it cool at room temperature (i never put my sponge in the fridge) when it is completely cool i fill it with soft ganche and cover it in ganache, then i put it in the fridge until completely hard. Just before i am ready to cover in fondant it i take it out of the fridge and leave it for about half and hour to an hour so that it has started to sweat because this will make the fondant stick. The gancahe has to be hard so that you can smooth your fondant and get neat edges. I never put the cake back in the fridge just leave it at room temperature but in cool room. The ganache is hard when it comes out of the fridge but once it gets back to normal room temperature it will be soft again. I dont know if you have heard of him but Paul Bradford does some amazing free tutorials @www.designer-cakes.com/free-online-cake-decorating-courses. He talkes you through everything and tells you ratios for ganache.
Keep at it, when i started out i used to get into a right palava, but as they say practise makes perfect :) x
ellie's elegant cakery
