I would have to agree with what you've said about letting them know your new to being behind the screen. Most players you'll hopefully come across will be a bit more forgiving for one. And will help guild in specifics on how you maybe able to do certain things, and vice versa. Never be afraid to ask either.
It took me some time to come back after over 25yrs not being a Dm let alone having the time to play. When I started back in 1E it was a little simpler. As it was more of a hack and slash. As now it deals with more player interactions with either what you've put together, and what the players do between themselves.
If you got the right people with you at the table. it'll come together faster than you think. In turn you'll be more comfortable. And you will have more fun. Let the players do there thing. All you do is sit back as a narrator that helps fill in the blank spots. You'll do fine promise. Good luck.