I taught the same course last semester and I plan to use the same Content, Discussions forums, and Grade items. Is there a way to add those to the new course without having to create each again?

Yes, there is a feature called Copy Components that will copy all but the student generated content from a previous course. It can be found by clicking on Edit Course in the course you want to add the content to. See our Copy Components quick guide or Copy Components video tutorial for more information.