paneled has a good view on this subject.... just know your limitations. And I could argue to get to know something about most everything on your boat. You need to be somewhat educated to make decisions as to who and what makes a good repair or mod.
Many of us have licenses/certification to do things and the license is required by law, like a doctor, lawyer, real estate/boat/insurance broker, etc. However, the license is NOT required if you do these things for yourself.
Perhaps you'll not do your own heard transplant, but you will bandage your wound, treat your cold, etc, and you perhaps will do some of your own legal work, buy and sell your own boats, houses, etc.
And, what if the professional that we hire got a D in that class and is not that good? We need to know enough to figure that out.
As for a marine electrician, I don't believe any certification is required, at least in FL, unlike his counterpart that works on your house. (but I'll stand corrected, if wrong).
I'm totally convinced that most anyone can get the skills that would be equal to that of a certified/licensed pHd in marine electronics, but that will take a lot of time and learning. But he could get enough info just by reading a bit or taking a course or two to be able to have a pretty good idea on what things to watch that would be a safety issue.