First of all, don't panic with your exam. You have studied for it during the year, now revised for it. You know more than you think you know and tomorrow when you get the exam paper in front you will remember loads of things about the subject, even if it is not clear in your mind now. You've still got a few hours to do some practice essays, they are a good way to connect anc concise the information in your head. Get a good nights sleep, and in the exam before you begin writing anything take a deep breath and read the question carefully before starting on the essay plan.
Secondly, your work placement will not expect you to be a full-out-professional, you are on a placement. Be eager to learn new things, but ask for intelligent questions, not the sort of questions you could find out by yourself really easy. (ie like here when people ask for stuff they could just as easily google themselves.) Dress neatly and take a suit-jacket in case they are formal. Shirt and tie is probs enough, but just to be on the safe side.
References would imply it is a written reference you have to present them, not contact details of references. Ask tutors or teachers, or maybe a reference from a previous work place. As for the original certification, there's not really much you can do if you don't have it. Explain them why and tell them how they can verify it. (Calling your school etc)
Don't worry, it'll sort itself out. Just concentrate on your exam now, then sort out references and call the work place to inform them about your certificate. Then start tackling your scholarship application. Work consistently until you've managed to get one thing out of the way and soon you've completed everything.