Becoming good at it does take time. But the fact is, as long as you're not planning to wow her with your sexual skills, you'll probably do OK. Awkward, but OK.
I wouldn't get too drunk. Drunk sex is already usually pretty haphazard. It might not hurt to give her the impression that you're a little, or a lot drunker than you actually are. That is if you want to try to keep your secret intact.
As someone else suggested, act according to what seems to excite her. Start off using your hands. I remember being fearful that a vagina would be hard to navigate my way around. Like I'd get lost down there or something. The "I can't find the hole!" bullshit. That's why I recommend using your hand and/or mouth first. Most girls like it as foreplay and it'll give you an opportunity to figure out how things actually work down there. It's not brain surgery.
Once you and her are actually ready for the "act" don't overthink it. Just do. Remember what your hands taught you, relay that to your dick, and go for it.
It'll probably be quick, but who gives a fuck the first time around. If it happens, and you're really nervous about it, just tell her you find her so ridiculously hot you couldn't control yourself as well as usual. That explanation will work wonders.
Anyhow, you're cherries popped! So who gives a fuck. You'll have it out of the way.
Your post made me smile. Thinking back to that time, everyone's nervous. Don't overthink. Just do. Good luck, man.
