Your Palmer and Colton text is a very good secondary source that contains a vast amount of material on what happened in the past. If your interest is piqued by any subject, Palmer and Colton provide an excellent bibliography and several helpful appendices. These primary sources should also help you to get a better feeling for the culture and the epoch about which you will be reading in Palmer and Colton. In addition, there are some secondary sources in the Sherman book that deal with historians' differing interpretations of some historical events. You should keep in mind that history is not truth.
Every historian sees history in a different light and has to choose what to include.
Sometimes a historical account may be based on less than reliable sources. Just imagine what Palmer and Colton had to omit. Imagine what care they had to take to get their facts straight. No history is a perfect retelling of the past, and your Sherman text will help you to see how history can be interpreted. This is not a course that will merely test your knowledge of names and dates, but will also ask you to interpret and to analyze that history.