Hi Tiffany,
We were using Moodle 1.9.9 a year or so ago ... when we uploaded the csv file we were able to change most things simultaneously. For example: firstname, lastname, city, institution, department, email, course1, group1.
"Course1" related to the course short name and "group1" related to the desired group allocated within course1.
We are now using Moodle 2.3.1 and this process still works well for us although automating this authentication/enrolment activity will be completed this year.