There really isnt much point in upgrading your MBA. The 13 inch pretty much just as portable as the 11 inch; although it a tiny bit bigger and a tiny bit heavier, its still an incredibly portable laptop. Also, the 13" battery life is about 2 hours (at least) better.
Also, although the 2011 model brings and i5 processor, if your only using it for school work, you won't even tell the difference between the C2D and the i5. Things such as word processors, Safari, etc aren't CPU intensive at all, and so the CPU upgrade would just be a number on a piece of paper that would really be of no practical use to you. Saying that, if you do things such as video encoding then the i5 would be a heck of a lot faster.
About the display...personally, I find my 13' display perfectly fine. However, if you want an external monitor, then the Apple Thunderbolt Display is terrific. It is expensive, and you should be aware that it is possible to use non-Apple external monitors (they are much cheaper), but if you have cash to burn the the TBD is beautiful, and the MagSafe adapter on it is really useful.
Wireless printer; great. You'll need it.
iPhone's are also really nice with iCloud, and other Mac devices. I sort out my days on my iMac, and then sync them to my laptop and my phone, so I always have a copy of what I'm meant to be doing somewhere. The notification centre on iOS 5 is a really useful way to see where your meant to be, and when.
Hopefully I've managed to help a little...
