There will definitely be a setting to show info on the LCD screen.
I never use 'live view' as Nikon call it, unless it is at night on a tripod, I use the old fashioned viewfinder.
Unless you really want the swivel screen I think the 550d is pretty much exactly the same camera so you could save yourself a few quid.
I don't use flash on any of my fish shots to be honest as I don't at this point have an external flash and the onboard one just doesn't work that well for the reasons above.
You are stood at the top of a very slippery slope by the way, the list of gear you want once you have bought the first lens and body just seems to grow and grow with each item getting more expensive!
I would recommend get the 'nifty fify' once you have learnt the basics, very cheap way of getting into fast, prime, glass.