I agree with the previous posts. I flew the 900 and she's a great airplane. But all of our initial training was conducted on the 200 model. I had a non specific oral guide, the one mentioned, and truth be told, it wasnt worth the money because it didnt help that much. As stated pay attention in class and you'll be fine. I am not sure how Mesaba conducts their training for the CRJs but many companies train on the 200 model and then you go through a differences training class for the other models. In my case it was for the 700 and 900.
And if you can understand the acceptance flow for the 200 and get it down you will be more than prepared for an oral exam in my humble opinion. I say that because it requires you to go through all the major systems. In my case I was asked system specific questions while I ran through the process. Again, just a suggestion. There is nothing wrong with wanting to get ahead and be prepared but the training department will give you everything you need to know.