kaplan LSAT courses are not the best example of available LSAT courses. for me, i lacked the discipline to study effectively on my own; the testmaster's course i took forced me to spend at least three or four hours a day working through LSAT problems. the instruction was also exceedingly helpful.
You can't fix your gpa at this point, but you can definitely work on the LSAT, and then in your apps you can say why your gpa is only a 3.19 (sick grandma? you were sick?) and explain the jump. I personally got a 155 the first time (those logic games made me freak and i couldnt think, i had to christmas-tree it) and then, with ONLY the lsac lsat book, i practiced for a month and brought my score up to a 162. I have a friend who took a kaplan course and got a 154 all three times (yes, 3!) that he took it, so I'm kind of... against spending $1000+ on a course that doesnt seem to help.