AutoCAD vs. ProEng.
Pro/E is a 3 dimensional parametric solid modeling CAD program. As such programs go, it is very capable, but priced much higher than its value and, comparatively, very difficult to learn and use.
eFunda is not really a source for CAD instruction.
The best preparation any designer or engineer can have for learning CAD happens away from the computer. Design happens in the mind. A CAD model is only a virtual shadow of what the designer sees in his mind. Learn and practice visualization. CAD is only a tool for capturing ideas.
I was fortunate. My preparation came from years as a machinist, starting at a young age, making 3D parts from 2D drawings in a family owned business. Now I can see what I draw and draw what I see.