It's actually worse than overkill--it makes you appear to be unfocused (on a career goal). It will appear to be the equivalent of a resume of a job applicant showing them flitting from one hospital/ position/ employer to another.
Sure, when you graduate you'll tell the CRNA program that you wanted to become an NP to improve your chances at admission... but they'll think, "first a nurse... then a nurse practitioner... now CRNA? What next?"
If you really want to be a CRNA, make every move appear that THAT is your goal. Take grad classes that will provide a foundation for that program, shadow someone, ask someone at the school where you'd like to go what they look for in applicants, then do it.
As far as your GPA, different schools
have different policies, but some allow you to retake the courses you did poorly in and they'll use the improved grade, others look at grad level classes separately, others average all the grades. Find out what formula is used by the school you'd like to attend and then do what would be most helpful.
Best of luck to you.