Don't bother with the faster processor. I have essentially what is now the lower end 13" MBP, and it is way more than enough for what I need it for as a college student (this includes Autodesk Inventor in bootcamp, which is a pretty hardware intensive piece of software). The faster one is just a spec increase, and that small of a jump will not be noticeable, especially for essay writing and web surfing, which is most of what college consists of.
You shouldn't need more HD space than 250 either. I am still trying to figure out what to do with more than half of mine, and if you actually do run out, get an external, they are cheap, you can partition them for backup and storage, and you don't have to take your computer apart.
As far as the next update goes, unless you are doing something really processor intensive (heavy video/photo/audio editing, etc.) there really is no need. You will be spending several hundred dollars on specs that you won't see anything from. Mine is already two generations old, but it serves me well, and I plan on keeping it until it dies.
I apologize for the length, but I wanted to be thorough.