You can freeze the cake beforehand if you want to save yourself a job but you have to make sure that it is fully thawed to room temp before you ice it because the condesation will ruin your icing and make it really hard to ice it.

I usually find a pic of the cake I want to do and then watch Youtube videos of the things I think I need to learn to do and then give it a go.

I made a Thomas cake for my DS1's 3rd birthday. It worked out okay. This was my first go with fondant and I just learned it all from watching Youtube videos (thank goodness for youtube) ... https://www.facebook.com/media/set/?...0fdb888&type=1

I also modelled it off a Thomas train that DS2 has. It is in one of the picture so we could see the scale of the cake to the train.

What cake are you making?