The best way for a CAD Operator to land a position at a Fortune 500 company in the Ag industry is to seek employment through staffing agencies. Unfortunately, health coverage is either over-priced or non-existent through such agencies.
The two main CAD packages used in the Ag industry are AutoCAD and Microstation.
Personally, I work in a process engineering department for a Fortune 500 company, after having gained several years of a wide variety of experience through temporary contracts.
I like my current position, because it exposes me to several different aspects of the equipment that I am involved with.