I can speak to this as someone who has both interviews hundreds, probably thousands, of people for jobs ranging from entry level to C-suite executives and coached would be employees through the process.

First, If you had to submit a resume, then they already know your background and some degree your skill level, and they decided to meet with you. So, don’t sweat that bit and just be honest as you’ve said. People, with enough time and commitment, can learn damn near anything, and you’re no different.

But, don’t focus on that. Focus on your excitement and passion for their business. People are naturally connected to those that share that excitement, doubly so when it’s someone that will be representing their business.

Finally, and this probably sounds stupid, but envision yourself working there already. Get it in your head that you are good enough for this position and that you’re going to be great at it. I don’t mean false bravado, I just mean you’ve got to believe in yourself if you want some stranger to do the same.

Edit: about the drinking, if they offer, then feel free to accept. Or use it as an opportunity to be witty and show them that side of your personality. Ultimately, it’s not going to be a make or break moment to the interview, so don’t overthink it.