My dad has been a inspector for 10 years in manufacturing he spent 15 years befor that working his way up. Now of days when they need a inspector out there they look for someone with 2 or 4 years of college, but when they cant find someone with the college they find someone from within.
I worked at the same place he does for 3 years and from what all I have seen from him and other inspectors it takes hard work, a eye for even the small stuff, getting all the certifications you can get that has to do with your type of work, and college is a big help.
I would have to say thats the order of it to. But I do think as time goes by that college will be higher on that list.