In order to make buildings for GE you need to know 1, 2, or 3 applications. Or maybe just 2.
Photoshop, Google Sketchup, and also this new thing called Google Buildingmaker are what you're going to need to learn. They take time to learn, and building your house can be as easy a making a box and putting stickers on it (or really really hard. It depends.)
Download Google Sketchup here