I'm in agreement with everybody else about the usefulness of the 50/1.4. I've tried using flash in an aquarium situation and it's a pain in the butt to try to avoid flash glare off the glass. As for the hood, go for one of the rubber screw-on ones--they're not that expensive. On the issue of ISO, with such a fast lens, hopefully you won't need to bump it up too much, but I tend to use anywhere from ISO 400 to 800--too much higher and then noise issues present themselves more prominently. Definitely shoot RAW--postprocessing will be a lot easier once you get home.
Have fun.
Heather