T.O.
Cakes are not hard. You can use a cake mix... but if you want to do it from scratch, don't worry.... just get the right flour and you'll be fine.
Better Homes has a great cake section this month. There a Valentine cupcake on the cover. They have 12 cake recipes in the magazine.
Frosting, you can buy it or you can make your own buttercream. It's not hard. To smooth any frosting, just keep a glass of warm water next to the cake while you frost, dip the knife or cake spatula in the water and smooth. Repeat. It's easy.
www.familyfun.com has lots of great cake ideas and party ideas. I think Hannah Montanna won't be on there, but something that goes with it... like maybe a record (cd) or microphone or just tons of glitter would be easy to do on a cake.