XNA can be a scary thing for someone new to game development. Many of the issues I have come across cause a lot of delay in my development, even if it is not a significant issue. Many times there is a simple answer but the fact that the XNA creator forums can be hit or miss on answers makes the learning curve drag out even longer. Recently I have made the jump to the 3d game space, introducing an entirely new approach to development.
Yes.. many of the concepts remain the same, just adding an additional dimension, but the biggest difference would be the assets you use in game. With 2D images, it is a simple one line import to XNA, with 3D it can become much more complex, factoring in polys, shader elements, engine requirements, deciding if you should even use a rendering engine, animations, bone structures, etc..
So many of the topics covered in traditional game development theory are based on 2D because of the simplicity of the material while the concepts remain the same, but even for someone who majored in a very heavy math focused degree, it was still a challenge to transition those concepts from 2D to 3D.
I am still learning each time I jump on to develop, but I am starting to get comfortable with the entire process from import to interaction of the assets. I was recently looking through my flikr photosteam and I realized how many mistakes I had to overcome in my game development interactions with 3d animations. Each picture represents an issue that I had posted to a forum for help. Many times the response time is 3 to 7 days. (Game development is flooded with questions so it is hard to get reliable solution help) Below are a handful of images that I had issues with in my growing pains of learning 3d model importing: