Photography - Basic setup for iMac screen and suggestions for Photo Apps

Received an Imac on my retirement (my children decided I should take on something new) that I will almost exclusively use for my photography hobby . Have no idea about setting up the 27" screen such as auto brightness, colour space etc. I have Lightroom and PS Elements but want to go into video, build advanced slide-shows and web galleries. All help welcome - thanks in advance.

--
TrevTheBrit
I remember using slide film...
http://www.flickr.com/photos/trevthebrit