I absolutely think you should take the job. If they sought YOU out based on your experience, accept, and take what you've learned and apply it at this company that is new to you. Remember that it is not the same as your high school, so you will need to be flexible and willing to roll with the punches. You'll be fine, I promise. It's a learning experience and even if they do consider you cheap labor you will only learn this profession by doing it.
I recommend you read through this site as well as stage management books you can get from your library, and learn as much as you can. Also, remember to sit down with your director and have a frank discussion about your role, what the expectations are, and your duties, as these can differ from company to company.
Break a leg, and keep us updated!