If you are planning on just using this for schoolwork I don't think you really need the top of the line 15 inch. Unless you are doing heavy duty video editing or photoshop work, the lower processor computer is more than sufficient. But whichever you choose:
2Gb is good for memory. 3Gb is great, but not needed, unless as I said before you're doing a lot of video editing or photoshop work.
160Gb is good for the hard drive, the 200Gb gives you more storage, but is a lower speed hard drive. But it's up to you.
Get yourself a copy of Office 2004 for students. This has Word, Excel, Powerpoint and Entourage (the Mac version of the Outlook e-mail software.) It isn't included so you will need to add it to your order. What will be included is iLife (iTunes for music, iPhoto for photos, iWeb for web pages and blogs, iMovie for movie making, and iDVD for burning movies.)
Glossy screen will be more like a television screen or an old fashioned monitor. Non-glossy has the finish of a flat panel monitor. I prefer the non-glossy because you don't get the glare.