Writing a basic 3d Modeler

I appreciate your honesty

I have to disagree with the AP.
This project might be a great opportunity to actually learn these concepts and acquire a deeper understanding.

Do some research in parametric generation of common shapes first. Start with simple platonic bodies such as cubes, tetrahedrons and so on. Find out what their basic properties are and how to generate the actual geometry from them.

Start with very simple algorithms first, e.g. don't care about faces and indexed vertices. If you can generate and manipulate simple shapes, start optimising the geometry by using faces and indexed vertices. You can read about these things in API docs and references such as the D3D docs or the OpenGL Redbook.

If you don't try to mimic the features of Lightwave, Maya, 3D Studio, Cinema3D and such you will most likely be able to create a simple shape and scene editor within a reasonable time.

Best of luck,
Pat.

Don't let that discourage you. There is a lot you can do with an API such as OpenGL and DirectX without a great deal of understanding of the math involved. First and foremost is having fun. Digging into the math, getting bored and quiting isn't better than knowing the API, but not the math. There may be some more advanced things you can't do, but as long as you are content with doing what you can do then it doesn't really matter.

There's a tutorial on gamedev that gives you code for MFC/OpenGL editor, it's really helpful