Most likely it will impact your career. Since we are in a draw down it could even be used to separate you from the service under certain conditions. I would encourage you seek advice from the local JAG office and I would also encourage you to read AR 623-3, as it pertains to the Appeal process for Academic Evaluation Reports.
The only way I know of having the AER changed is to conduct a Commander’s Inquiry or a formal appeal. The odds of them changing the report are slim, but it is possible if you can support your position. More importantly you will need to obtain credit for the course and you can only do this with a 1059.