The official University of Illinois policy related to academic integrity applies; see the Syllabus section for more details. Any violations will be dealt with in a swift, fair and strict manner.
Your group work must be your work as a group, and done independently of prior work by others. Do not submit work done by others as your own. How you divide work within your group is up to you, but you should state this at the end too (see above for marking).
Use of external resource is permitted provided the work is appropriately cited and referenced, and that you are extending it / building on top of it.
So in summary, do not cheat.