there is an outfit called irrigator tech, I think and I am scheduled to take an advanced class next month put on by a local supplier.
Two years ago I luckily found a retiring irrigation contractor and hired him to do a few jobs for me, while I looked over his shoulder and helped out with the grunt work. Then once I obtained my irrigation license, I hired him to look over my shoulder a couple of times and finally I just started flapping my own wings and the jobs come out great and are a lot of fun and very satisfying to see the water spraying just where I want it. And so far I have made good money with irrigation.
I also went to a seminar put on by our local materials supplier to learn the basics.
Next month I will purchase a van to ourtfit with just irrigation tools and parts so it is ready to go at a moments notice. I try to keep enough inventory to do one project, ie DVC, controller, valves, boxes, fittings and pipe, etc.
Right now I have everything in 6 tubs plus pipe, to load in my pickup and go. But I want to get this van outfitted and roll.
By the way have you heard of Durafittings. If not you're really missing out.
Hope this is helpful and good luck.
And in answer to your original question, I think training is always worthwhile. Sharpen your saw!