AI intend to make my daughter's birthday cake this year. The theme is Mickey Mouse Clubhouse. I've made cakes/cupcakes before, but never anything really fancy. So, I want to make a fondant cake. It would probably be a three layer cake with the bottom being square/rectangle (the grass), the middle a dome shape or circle (red clubhouse) , and the top a dome (the mickey mouse head and ears,no face). Since this is the first time I'm doing anything like this, I just wanted some advice. For example: what tools I need, when I should start prepping, should I make a trial run of the cake itself (from what I heard WASC is the best), should i use premade or home made fondant, what do I use to color the fondant if necessary (food coloring?), what bowls are the best to make the dome shape cake, what measurements do you recommend for the cake (as in cake pans; for about 25-30 people), would a single layer of cake for the bottom (square/rectangle)withstand the weight of the rest of the cake, etc. Any help would be greatly appreciated.

I did something like this....I used the half ball pan for the head/ears (serves 8).   It has a 6" base I believe, so I put it on an 8" double round (serves 28-wedding) and if you want your bottom a square you will need a 10x10 single (that serves 20)  I think a rectangle wouldn't look good...so you are going to have more servings than you need...but if you want a 3 tier cake with the design you described, you will have to go over your servings.

WASC is a good recipe to use. 

I buy my fondant because I use so much.   When I started out I made my own MMF.   It's the cheaper route.   Color the fondant while you are nuking the marshmallows.  I  use Americolor gel...Wilton is too diluted and you will need a ton.

If you have never stacked a cake before, go to the wilton site and read up.  Also find some youtubes so you can get a visual.   If you stack/support correctly, you can stack a 25 tier cake.  The cake sits on your support. 

Oh...if you don't want to stress about making any boo boos....you might want to do a trial run on whatever you are really nervous about. 

Good luck and post pictures!