I would only get a second bachelors in nursing if that is something you are interested in. As far as helping you out with med school admission, I don't know if it will. My undergrad major was biology and I graduated with a 3.0 (too low for medical school admission). I then started a nursing program as a second bachelors and had a 3.8 GPA. When speaking with several medical school admissions directors, they told me that the nursing degree was not enough to improve my application file. The recommended that I increase my core science grades. Soooooo, then I entered a biomedical science post-bacc program and maintained a GPA of 3.8. This is what will impress the admissions committees at medical schools. If I were you, I would skip the nursing route and go the post-bacc route (unless you want to do nursing). If, however, you are using the nursing degree to get into medical school, I would skip it and go for a post-bacc program.
PS- The ~20 or so credits that you take during the post-bacc programs are all science (same as the 1st year of medical school). The science credits are reflected as UNDERGRAD science grades. This means that if you kick ass in the post-bacc, you will singificantly raise your pre-med science GPA. It's hard, but if you want it, you'll do it.