How far along are you as an undergrad? The LSAT is weighted more heavily than any other admissions factor, but your GPA is still important. As an undergrad, the best thing you can do for yourself is maximize your GPA and prep sufficiently to post a strong LSAT score. For most T14 schools, 3.5-3.6 is around the 25th percentile for admitted students. It's at the 75th percentile for Marquette, and below the median of 3.7 for WUSTL. So if there's time, boosting your current GPA will improve your chances significantly at the kind or law schools you're interested in.
I suggest reading up on law school admissions and employment prospects on some of the other boards out there, as well as searching through past posts here. You mention Marquette - I don't know anything about the law school, but certainly investigate how well its grads are doing professionally in the type of law you'd like to practice.