what is your LSAT (if you have one yet?)
IF you don't mind wasting the credit time I would go ahead and take the class again. I doubt they would look down upon it. I retook a class I withdrew from f-man year and I don't think it hurt me. But honestly, if your LSAT is decent a 3.7 is still a great gpa, and micro is a crappy, boring class that you will have to sit through with a bunch of freshmen. Taking boring freshman-level classes senior year has, at least for me, been a real downer and produced my first B+. So from one GPA-conscious 0L to another, I would let it be and get As in classes you are actually interested in.