If you don't already know how to make 3D games for the PC using OpenGL, you won't know how to on the 3ds.
Sorry for derailing you, but I can create 3D homebrew without any prior ogl knowledge, only using a custom per-pixel framebuffer renderer

Or if you're very good in maths, you could abuse sf2dlib as sf3dlib by creating a rendering engine, that draws fake 3D-like panes by calculating the panes' edges' 2D co-ordinates manually
Edit: if you want to use polygons'n'shit, then you'll need to have prior ogl-like knowledge and experience, but if you're only drawing panes, then you can use my technique
