Give credit where credit due.
Home Depot, if available has seminars, at least in my area of Califonia on the do's and don't's of irrigation. You might want to check there. I've been doing installs for over 20 years, I was inpressed by the class. I went to the seminar to see anything new in installing.
On the contractor liscense and learning, go work for somebody else a couple projects. See if a local contractor will sponser you. Experience is the best teacher.
J-LC Landscaping & Maintenance Gardening
C-27 CA. Contr# 770044