OP, I had a very similar concern when I returned to the game. I was very unsure of what I was supposed to do, the pace was beyond me and the instructions didn't always feel clear.
I was worried about screwing something up, and met with "just ask." A year later and I've kinda figured out that it's not that critical. Just follow the herd, do what the raid leader says and if you are lost, do nothing. You won't understand what is happening, but you won't screw it up.
You won't get a lot of insight or on-the-job training during the raid instructions because raid leaders function more like shepherds than field training officers.
Whenever I have asked one of them a question as an aside, they have given very thorough and helpful explanations.