oh, to the second point of your question...
how "hard" is it to reach your goal of lets say a 156.
this, of course depends completely on you. are you naturally predisposed toward the LSAT? are you naturally intelligent?
if you answer YES! to both of these then my answer would be to you that these are fairly easily attainable goals. i scored a 156 exactly the first time i took the test having never seen an LSAT question in my life and not knowing what to exspect. im no genius, so if you've got a head on your shoulders i think you can fairly easily accomplish this. on the other hand, if you struggle at standardized tests or logic pinciples it may be a bit tougher for you. hope this helps.