I started out in eastern Nebraska in the late '60s. And I did a little work in northwest Iowa as well. I know how loose the regulation can be.
I think Sparky66wv's advice hits the mark. First, get a copy of the NEC Handbook. The additional illustrations and explanatory text go a long way. You can find used copies at www.bibliofind.com
after searching on the words National Electrical Code
Then, with the Code beside you at the computer, look up the Code sections talked about in the threads that interest you.
Your life experience counts for a lot. In my opinion, you'd waste a lot of time covering ground familiar to you in a structured course. The real meat is in the actual words of the Code connected in your mind with the recollection of all the work that you've done and do. Start off paying attention to the wiring method you are most familiar with. Pick one: NM, PVC, EMT, whatever, and read the Article on it and look up threads related to it, new and in the archives (they're huge!). Then expand your choice of articles.
Let your interest
in the specifics be your initial guide. Do it frequently, and, with the passage of time, you'll get the rewards.
Personally, I'm amazed at how much I get each and every time I revisit the basics, let alone the complex stuff.