Getting your CNA is a great idea. I'm from WA state and we are actually required to have our CNA liscense before we even apply to nursing school, it is a prerequisite. Not only will you get background knowledge before your nursing courses but you will have practice doing skills you will need to know. Where I am from, you should already know how to take BP, put on TED hose correctly, do an occupied linen change, change briefs for incontinent patients, bed baths et cetera because these skills are not taught in the program.
Getting in there and getting your hands dirty and knowing these skills and how to do them well will make you stand out in class and clinicals since you will be comfortable doing them. From personal experience- When I was in clinicals there was a girl in my class who did not want to change a patients breif and her nurse heard her say that and lectured her about not being respected as an RN if she was afraid to change breifs.. obviously there won't be a CNA there 24/7 when you are an RN to do all your dirty work and you should be expected to know these skills.
Thats just my 2 cents =)