3D Printing

So in my engineering class (I am in high school) we have a final project due by the end of the year. Obviously, I have a lot of time. The engineering program at my school is fairly well funded by the state, so we got 2 new 3D printers. One is Arduino based, and the other is a MakerBot Replicator 2. As you can tell, for my final project I want to print a yoyo. I have experience with CAD (we will be using Autodesk and SolidWorks), but I don’t know much about designing a yoyo. I know what makes a design work, but I don’t know how to go about designing from the ground up. Any tips?
What I am aiming to achieve:
-As few parts as possible
-A way to integrate the axle system
-Use spacers instead of designing a bearing seat (too hard lol)
-Stability/weight (this is the hardest part :-\ )

Here’s some info on one. Perhaps send the OP a PM, he may be able to help.