For your point 1, the mouse gives a position in 2D and you need a 3D position in the 3D picture control.
You can use the method of the 3D picture control: Pick Model. This method returns the name of the models that are intercepted by the projection of your view in the direction of the window coordinate that you provide.
You can extract a mouse-click coordinate in the 3D picture control by using an event structure.
You can display text in a 3D picture control by using Create Text.vi.
For your point 2, only you know how you can get information to automatically positions your sensor. Your question needs to be more specific.
Marc Dubois