I was always curious - is it possible to play and enjoy KOTOR, if you never ever watched and liked Star Wars and you actually don't know the universe? I heard great opinion of the game, but it was always the only one in crpgs Top 100, which I never even considered to play...
It's set thousands of years before the Star wars movies, you don't need to have any knowledge of the Star wars universe to play it.
However, I'd say it does help if you like Star wars, it captures the general atmosphere pretty well. Personally I was somewhat disappointed by it because I'm not that much of a Star wars fan, gameplay wasn't that great imo (combat is hardest in the beginning, becomes pretty easy later on when you're a Jedi).
The difficulty level descriptions are so damn vague. "If you are first time player, select Normal"... ok, but what exactly is different between e.g. the Normal, Hard and Realistic difficulty levels?
Realistic isn't that hard...you die easily, but so do your enemies, so if you sneak around and ambush your enemies, aim for headshots etc. you can take them down without that much of a problem. But don't expect to just storm in with guns blazing and gun down dozens of enemies head on, that will fail.
Normal/Hard is more like normal shooter gameplay, with your enemies taking several hits to die (that is they're becoming more like bullett sponges), but you can take more damage as well.
I'd go with realistic.