My first occasion cake....HELP!

My little brother turns 18 on Thursday and I've volunteered to make him a cake. I've decided on a theme and bought a transfer to put on the top. I've found a new shiny cake tin at TKMaxx for it. If I do two layers it should be thick enough.

Now all I need to do is practice the making of the sponge and some decorating techniques. My icing skills are something that in all honest, I'm rubbish at. I don't have a steady hand or an eye for detail. But I am determined to make this look good.

So what can you teach me? How thick should the layer of icing be on top? I think I have to use Royal Icing, is this correct? Is there anything I should about applying the transfer? Jam or cream to bond the layers?

HELP ME!! I am now scared it's all going to go horribly wrong and I'll look like the worst sister in the world, which won't take much doing.

Pass this post round any baker that you know. This is an SOS

It hopefully will look like this

and not this...

Thank you in advance x