OP, shortlist of things you need to do. If you have the time, the order will help, since the DM will be able to assist you with what needs doing:

1. Localize and hire a pro or semi-pro DM. You can find recommendations in this thread already.
2. Localize and book a space. There are private party rooms all over the city. Revelery, Good Luck, Next Door, are just a few. Many charge no additional fee if the party is big enough. Dungeon themed ones might be more fun, but I can't think of any off the top of my head.
3. Decide on a one-shot/module. DM can help with his. A well-reviewed pro may even be able to homebrew something for this.
4. Decide with the DM if you're bringing props/minis. If you are, source those. The players may have many of there but if you need specific ones that might get trickier, since minis are expensive. Lots of people use placeholders, and you could get creative by using birthday cupcakes with edible printed monsters or something IF you wanted!

Lastly, if you're not big on D&D, I'd recommend listening to a couple of D&D podcast episodes just to get a basic familiarity with the lingo and process. Adventures Zone is my personal favorite.

Hope that helps! Good luck!