Buying my first mac

[r3ac7]

So long story short, throughout the last two school years I've done good, both in school and work, so my parents decided that I finally deserve a new computer(my old one is like 10 years old). I've wanted a mac since a long time, so I wanted to ask some questions before I buy it. The Mac will be used for school work(office), surfing the web, music and videos, some photo editing from time to time(nothing heavy).

First of all I want to say that I want to get the MacBook Air 13' 2012 i5 1.8GHz 128gb, but I'll probably upgrade the ram to 8gb, because 4gb is a bit low.

So, I'm in 11th grade, which means that I won't get the student discount, right?
I have a friend though who goes to college, is it possible that I could get the discount if she comes with me?

The MacBook Air that I want, here in Canada is $1199(with 4gb ram) and $1299(with 8gb ram). How much will it cost if I get the discount?

Since I want this computer to last at least 4 years I was wondering if this specific computer has some problems after some time of usage. What I mean is for example the MacBook white 2007 had a problem with the casing, or the MacBook Air 2008/2009 had a problem with that part around the display. Does the MacBook Air 2012 have anything like that that I have to worry about?

Can I get the ram upgraded to 8gb, without making an online purchase? I want to purchase it from the store. Is it possible?

That is all for now, sorry for my stupid questions(I know they are), but I've never purchased a Mac before, so I need some advice.