Thanks in advance for any advice!

I am wondering when I should buy my new Macbook, and if I should get any upgrades.
I am a teacher, will be new to Mac, and am looking to buy my Macbook sometime by the end of Sept. I will be using it mainly for work (documents, possibly spreadsheets) and internet use, with some minor photo-editing and iTunes use. I do intend to be working abroad within the next few years, and would like it to last at least four to six years.
Reading different posts, I am a little confused about whether I need to upgrade memory, hard drive or anything else. I am currently considering the Macbook 2.16 Ghz, mainly because I want to be able to burn dvds as well as cds (as I can on my desktop). Any thoughts?
Am I better off buying it before the educator's discount (free nano, etc.) expires mid-Sept, and using the time to get used to the OS X environment? Or should I wait until Leopard comes out? Would I miss out if I don't get Leopard? I won't be upgrading to Leopard if I buy now. Or is there a significant chance the Macbook prices will drop after Leopard's release?

On a different note, on my current pc, I have software called Deep Freeze installed, which I love. It is not an antivirus program, but essentially (as I understand it) restores my hard drive to its initial 'frozen' state with every reboot. (I can turn it off to load new software, then turn it on again.) This program has kept my Windows environment relatively problem-free. Since I will be running Windows to access my years' of work in Word documents, will my MacBook be exposed to typical Windows problems? Should I install Deep Freeze in my MacBook?
I can't wait to get my first Mac!