For me, Python is always the best language to start learning how to program. Its where I got my start! I'm not so sure if Python is suited for 3D programming. But its still the best place to start learning the very basics.
Game Maker is an ease-to-use game creation tool that can make both 2D and 3D games. But its 3D capabilities are a bit limited and very advanced.
Many people recommend using C++. And many of the greatest 3D games were made with it. And since you already had an introductory course on C++, I don't think you would have a hard time learning one of the best languages out there.
XNA is also a good place to start (according to some) and its great for 3D games. And it uses the C# language, which I believe is great for beginners.
If you are really serious about your game idea, then learn a very easy language that you're comfortable with. Then, once you have mastered it, move on to a more advanced language that is great for 3D, like C++.