Congratulations...this is great good news!! You will be fine and after the first days you will feel fine and it will get easier. Those first days are freaky and hard because you are the "new guy"... I am So pleased for you. Find the people who smile & enjoy this company. Don't worry about pretending about a "personna". Be yourself. Obviously you are the man for the job. Remember not to listen to all the weird stories or make snap judgements about your co-workers, that never helps. Do your job the best you can. Ask a lot of questions - new people do that.
Take it step by step.
If you stay open minded - you'll do well. Again, Bravo for YOU !!!!