You'll be alright 2D and 3D space are vastly different as far as how you percieve your object. I draw and paint a lot but 3D is different, almost easier. Perspective and foreshortening are automatically handled so focusing on true 3D shape is all you have to do. Once you can grasp whatever program's interface and tools you'd be surprised of what your capable of doing. Modelling is not difficult as long as you persevere.