I think you're making a good choice with the MBP over the MB since you'll be doing graphics and video stuff. Here are my thoughts on everything else you mentioned:
- The speed difference you'll feel between a 2.4ghz and a 2.5ghz machine will not be very noticeable. In my opinion, it is probably not worth the $500. That seems to be the consensus from others in this forum before, but confirmation from someone else would be helpful.
- I'd recommend 4GB Ram for your MBP but DO NOT BUY APPLE RAM. It's a waste of money, you can upgrade it yourself from Crucial for $100 less at least for a paired set of 2GB sticks (or buy a single "unpaired" stick for about $50). Apple's installation costs are not worth the benefit since popping ram in and out is a piece of cake. Plus there are many tutorial videos online... If you don't want to mess with it that's fine but you should look at a
self installation video on youtube to judge if you'd be comfortable replacing it yourself.
- The hard drive question is a little complicated. People have debated the performance of the 7200RPM HDs and whether they are worth the upgrade over the standard 200GB or an upgraded 250GB. Some say the higher speed reduces battery life, which I cannot confirm nor deny. Others say that the speed benefit you get from the faster drive isn't very noticeable, so if it were to reduce the battery life it may not be worth it. Since it's a portable and you want it to last through college, I would suggest going with the 250GB upgrade rather than the faster drive. It's greater capacity will definitely be a benefit to you, and since it only costs $45 it's pretty cheap
- In regards to the buy now/buy later, I say buy now. I don't believe the Montevina upgrades will be available before your college starts (assuming end of August), and certainly not before the free iPod deal ends. You should buy now, sell the iPod if you don't have a use for it, and enjoy a great MBP. Furthermore, the major performance upgrade will come with the Nehelem processors that won't arrive until at least January.