Is it worth repeating College courses that receive a bad mark?

I recently finished my English Composition 2 cl expecting an A-. My teacher however gave me a Zero for our final essay because of a MLA citation error which she equates to being the same as a deliberate plagiarism. This leaves me with a final grade of D+ which is ping at my college. However, I am a Dean's list student surviving on Financial Aide. Should I repeat the course in order to receive a higher grade or would it be a waste of money since my GPA should still be over 3.0?