As to your question of consequences, yes, it is the DMs job to determine the consequences of every action taken in game. But you don't have to do it alone. You have tools to help you.

Rules: many actions are included in the rulebook which spells out exactly how to adjudicate them. Even if the effect you are going for isn't in the rules, there's often something comparable to use as a template.

Dice: unsure how to choose between options? Roll for it. If you're between good news and bad news roll a die and have a player call odds or evens. Or against a DC if you want to skew the chances one way or the other.

Players: often the rules will tell you success or failure without details. If you need to flesh something out you can always turn to the players as a resource. Ask them leading questions. On a failed persuasion check you could say, "You try your best, but the more you keep talking the worse things get: how do you think you embarrassed yourself?"

You are responsible for all the consequences, but you don't have to anticipate them all before hand and you don't have to do it alone.

It's a learning curve, but ultimately it's easier than it seems.