In my humble opinion, sous vide is great for certain applications/situations, but I have yet to have a perfectly SV cooked steak that is better than a perfectly grilled or conventionally cooked steak.
As for learning, I think it's a complicated but learnable topic if you are trying to learn it thoroughly. If you want to just get your steaks out down and dirty, it's not as daunting. Whatever works for you.
-I suggest you learn all the different parameters (thickness, initial temperature of the steak [straight from the fridge or room temp], temp of the grill/pan, total cooking time, pan roasting time, resting time, when do I need to have it in the window, etc) that are involved.
-Each time you cook steak, use as many methods for checking doneness as possible. If possible, cross reference - use a thermometer, see what it looks like, Notice when the juice starts to come up, poke/pinch it, compare it to your fist or palm or cheek, and try to "calibrate" all those things together. For instance, 135 degrees looks like _________, it feels like __________, etc. Since you may not be able to use a thermometer on the line, you'll have built up experience with touch, cake tester, etc with some amount of reliability and repeatability.
-Try to be systematic, minimize variables, and try to get some feedback where possible. Preferably not from refires, ha ha. Buy a few steaks and have some friends over. Instead of each person getting one steak, practice cooking them different ways and everyone tries every steak.
I find it helpful to think about how to create the effect you/the client wants. Probably 60% of people want medium rare. But some will want Black and Blue on one end or dead, dry, hammered well done on the other end. Should you start it really hot and move it to a less hot part of the grill? Should you just sear it? Should it go at a somewhat lower temp for a longer time? And so on. Eventually, you'll know several ways to have a steak come out any particular temperature, just in case you need to cook a well done filet in 3 minutes or a skirt steak rare in 25 minutes. And you'll know when to use what strategy for the situation. Hope that helps.
I go through a whole spiel with my students when we do steaks, whether on the grill or in a skillet. I give them very valuable information but I think that when it comes down to it, if you aren't doing SV, it just comes down to experience. After you've done a few hundred steaks, you get a good feel for it.
I know I'm late to this discussion but I thought I'd mention a trick I learned from a cooking show while we were stationed in England. If you hold your hand out in front of you with all fingers extended like a high five, touch the tendon between your thumb and index finger. That's what rare should feel like. Now, take your index finger and hold it to your thumb like you're pinching something. Feel the tendon again, that's med. rare. Add the middle finger to the pinch so you have 2 fingers down on the thumb in a pinch. Touch the tendon again, that's medium. 3 fingers= med. well, all fingers pinched= well.
After you've cooked many a steaks, you'll know just by the finger poke but this was the way I learned how to cook a steak perfectly every time.
Edited to add: I hope this description makes sense. It's easier for me to show you than it is to explain it.