For now, I would suggest openGL, as it is easier to learn. Google
tutorials for it. This (http://www.videotutorialsrock.com/) link
would help you get opengl installed.

Well to make a GUI program in opengl, say a basic triangle, all you need
to know about c++ is, functions,libraries,if-else,and switch-statements.

From that you can make your first triangle....

Ok whats the problem. In your drawFunc have the (X_i,Y_i,Z_i)
and the (X_f, Y_f, Z_f) as variables and change it accordingly. Maybe
if '+' is pressed, increase the length of each X coord by 1...

Ask your question in a clear and concise manner.