I have a new class list and am wondering if I upload it there will be duplicates, will it just take the new information or will it overwrite what is there now.

If the classmate is exactly the same, there won't be duplicates. If they have changed at all, you will have duplicates. If you want, you can reset those classmates. That way, all of the classmates will be uploaded new.

The RESET sounds scary, but it will let you choose only classmates who haven't joined yet and delete them from the database. The RESET CLASSMATES is found on the Manage Classmates, Upload Classlist, then RESET CLASSLIST. You will be given the option to select a few classmates.