Can the "Area Sum" integration event (in Chemstation) be replaced by the "group peaks" function (in Clarity)?

Yes, it can. However, the philosophy of use is slightly different. The peak areas of a selected group of peaks are summed, and the group can be named and calibrated as a single compound. Please refer to the corresponding parts of the Reference and User Guides. Especially in the calculation of the Result table Total line and Amount % column, there are potential problems, if the calculation procedure is not understood correctly.