I taught Maths for 15 years, so here's my opinion:
If you only got an F first time around, there's probably not a great deal of chance of you getting an A or B at your second attempt. (That obviously assumes that you weren't absent for most of the course, e.g. with a long-term illness). However most employers (or further/higher education establishments) ask for an 'A to C' grade, so there's little point in retaking the exam if you can't get a grade C.
The 'higher' level of exam entry offers the chance of getting an A, B or C. (I think that you'd probably find that course very hard). However the 'intermediate' level offers a C, D or E. That would seem to be a much more suitable course for you but you'd need to remember that you'd need to be a 'high-flyer' within that group in order to get a C.
Chris