Do I now have the knowledge to set up Unix networks for big companies?

I agree you have to know how Big bussiness's work and the security policies and proceedures. You can do Courses at Tafe or more intricate courses at Uni? A lot of big companies may re image their servers every night, use hardware/software server firewalls to save resources on the PC, remote updates or reformats on PC's or multiple reformats, has to be done in a down time and you have to know how to do it from one PC, rather than indivdually. big companies have a lot of sensitive data, so you have to have be squeaky clean and possibly require a police clearance, strike up a security policy to be signed by you and your prospective clients which is a binding contract.