1. Taking the harder classes at junior college (during the summer) will make it easier, but your school will have it's own rules about that. They may not allow classes that are part of your major to be taken at another school (many schools don't). The only other thing I can think of is don't take so many hard classes at one time...take one fun class if you can. I start at a 4 year school so I don't know many tips yet
2. BS-I'm not sure of what you could do with a BS. Maybe some work in a lab.
MS/PHD-research, academia
MD-hmm not sure. Obviously you would go to med school and probably specialize, so I'm not sure how it would relate to neuroscience exactly. There are PhD's in medical neuroscience that focus on stuff like strokes, parkinsons, stuff like that. So you can do medical related without getting a MD. But neuroscience is a good undergrad if you want to go to medical school and become a psychiatrist or something.
Neuroscience is something I like a lot too, but also don't understand much about what careers there are available in it.
http://www.indiana.edu/~neurosci/
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After a time, you may find that having is not so pleasing a thing, after all, as wanting. It is not logical, but it is often true.
--Spock