Vegas Baby!!!

We're going to Vegas! I am so excited!!! Its our first vacation since our honeymoon 3 years ago. We are going in March so its about 5 weeks away,let the count down begin. Our friends Stacy and Johnny will be joining us and they have never been to Vegas either. Its been forever since I have flown so my mind is overwhelmed with the typical, what should I pack, one suitcase or two, what to put in the carry on, how will the weather be? I wear myself out with the over thinking before we even leave. Its a really bad habit of mine, but what do you do. I'm a huge list person so that will help me focus and feel better. Since we have never been to Vegas if anyone has any great things we should DEFIANTLY do let me know:) Thanks!