Well, I'm not exactly in the graphic design field... I'm actually a senior biotechnology student (which, admittedly is probably graphic design's polar opposite) but I have done some amateur editing work through school and almost everyone uses Macs except a few (stubborn!) people who simply will not listen to reason.
I'd recommend talking to an academic advisor at your college about your major though; they should be very willing to discuss the opportunities in the field and what will be required in the program. Get to know these people, or a specific person in your field that you can come back to routinely! They are (and will become more so as you go along) instrumental to your success in any post-secondary institution.
Oh and I was wondering if there is a command prompt, task manager or any sort of thing like that, and is there anything I should know so I can become more familiar with a mac?
There is a command prompt, being that Mac OS X is built on Unix. However, it will not work the same way as you would expect a DOS (or later, Windows) command prompt to work. The commands will not be the same. I don't have (really) any knowledge of command prompts, despite being what I would describe as a fairly "prosumer" user who knows a thing or two more than the average person would. It really is not necessary in OS X, at all.
Same thing for a "task manager". I'm not sure what purpose you would have for one of those? The Dock in OS X functions as an application launcher and allows you to monitor running applications, and quit them.
All in all, the Mac is much more intuitive than Windows (IMHO) and so there is not much to really explain to most people. You seem to be fairly knowledgeable (or savvy) with computers off the bat so I doubt you would have much trouble (if any at all). The basic concepts are all the same across the platforms because Microsoft stole all the basic ideas a couple decades ago. I'd recommend taking a look through Apple's Mac OS X pages at
http://www.apple.com/macosx
What kind of programs would I use for graphic design so maybe I could try them out on my mac once I get it.
Basically any program that you could use in Windows in this field has either a Macintosh version or a Macintosh equivalent. Photoshop is obviously the big one but there are others. I don't know much specifically about these applications (Photoshop is all I've really used) but rest assured that there will be applications for your purposes. Perhaps there are other, more knowledgeable posters who can chime in on this matter.
is there anything that I can do to increase the battery life other than not running it on the NVIDIA video card and lowering the brightness? I heard of battery cycling?
Not really. The 9600M GT and the display are probably the two largest battery draws in the machine. So, unless you are doing 3D rendering, the 9400M is probably the better choice. When you need to do renders, you'll probably have the machine on a desk plugged in anyway, so you can activate the 9600M GT without having to worry about battery life. You'll find that the MBP display is quite bright; even in daylight conditions I rarely run mine at maximum brightness. At school when I need battery life I don't find it inconvenient to run it at 1 bar of brightness either. Of course, calibrating the battery on a regular basis will provide you with a more accurate readout of the remaining battery capacity, but will not actually increase battery life.
Any more questions? Feel free to keep them coming, and I apologize for the length here.
--Travis