Where can I get a 3d example in OpenGL 3.0?
OpenTK provides the same low-level API calls to OpenGL, any tutorial covering OpenGL 3.0+ will work, just turn gl*() calls into GL.*() calls. You also don't have to worry about window/context creation, as OpenTK manages all of that for you with GameWindow/GLControl if you choose to use it them.
As for a good tutorial, I would recommend this one: http://www.opengl-tutorial.org/
You can skip ahead to Tutorial 2. Create a new subclass of GameWindow and override OnLoad, OnUpdateFrame, OnRenderFrame, and OnUnload instead of going through tutorial 1. There's a guide for all of that somewhere on this website.
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