There are certainly no courses in high school that will better prepare you for Neurosurgery than for any other medical specialty, like Pediatrics, for example. First you need to get into college, do well there, and then focus on getting into med school. Knowing this, you can prepare for college by taking chemistry, biology, physics and advanced math courses. Take AP classes, if your school has them. At my college, students who had taken AP science courses did significantly better in introductory classes than those who had not. If I had known this, I definitely would have taken AP Biology in high school. In addition, AP classes might pass you out of certain pre-requisites for your major. In my case, I had enough AP credits to finish my Psychology major in about 2 years, which let me double-major in Neuroscience.
If you are interested in Neurology/Neurosurgery, you might want to check out some books by a doctor named Oliver Sacks. They are fun to read and might be a good conersation piece with college interviewers.... "Actually, I really want to be a Neurosurgeon. I have always been interested in Neurological disorders and I'm a big Oliver Sacks fan..." That sort of thing.
As far as colleges go, I don't think which university you go to is necessarily as important as how well you do there. With that said, apply to a number of schools in your range, and go to the best one you get in to. You will probably find schools with strong science programs to be more enjoyable. You don't have to be a science major, but you will need (in general) a couple years of chem, a year of bio, a year of physics, calculus, molecular bio, genetics, and biochem. Also, many med school applicants do research experience while they are in college, so if you go to a major research university (as opposed to a small private college or a small state school) you will be more likely to find a professor who will take you in under his "wing".
I can't tell you about med school, I'm not there yet!
I think it's great you are focused this early. I wish I was! Good luck.