Mackbook Pro retina 13" 2013 8GB RAM or 16GB RAM? i5 or i7 intel processor?

I have been looking at Macbook Pro's for awhile now and I still can't decide what to get. I can say that I'm pretty much set on this Macbook but not the upgrades.

8GB RAM or 16GB RAM and which processor? I have done research and read other discussions about similar topics but I still cannot make a final decision.

I will be using it for school work, mainly writing essays or making powerpoint presentations, and also other things like: Using the Internet, watching videos online, and others stuff. I also plan on buying the Apple USB SuperDrive to watching DVD's and/or download some of these movies onto the Macbook. I will also be using some sort of external drive to hold most of this movies to save space on the macbook, but my main concern is picture quality and computer speed

I will most likely have this macbook pro for the next 5-6 years before I think of buying another so long-term upgrades are necessary since I cannot upgrade this after purchase.

Lastly, I have done research and I have also visiting an Apple store to try this macbook out but from your experience how much better is the picture quality on a retina compared to just a normal macbook pro? Is it a very noticeable and pleasing difference?

ALSO: I hoping to keep the price as low as possible to suit my needs, so both the 2.8GHz Dual-core Intel Core i7 processor AND the 16GB will make it too expensive BUT if its truly worth it I will consider it.

Sorry that this is so long, this is my first post so I'm not really sure if I did this correctly. Thanks for any help