That’s why we’re here, standing around the digital water-cooler.

My experience (and length of same) is similar to yours.   (My feelings about mainframe software ... ;-) ... might be a wee bit different ...)

And, let’s face it ... “it’s what you know, and what you don’t know yet.”   The learning-curve, of any computer-related undertaking, is both difficult to ascend, and strangely easy to forget.   This will be a snap for you, of course, but ...

Alice, Revisited:

“Begin at the beginning, then go all the way to the end, then stop.”
“(Wise ass...)   But where is the beginning?   This manual was produced: (a) by IBM, (b) on a line-printer, (c) thirty-five years ago ...”

(Sorry ... ;-) :-D ;-) ... I couldn’t resist ...)

Been there, done that, still got one around here someplace.   System/360 Principles of Operation, I think ...