You don't need to buy a blu-ray player seperately. However, I do recommend you get a blu-ray player for viewing movies. I am currently using a PS3 as a blu-ray player. I watched couple of movies on my LG Smart TV and blu-ray is where you can actually view the depths of your TV. A blu-ray is not mandatory, but I do recommend it for great viewing.
No; you don’t. If you can afford it, good for you; else you can buy a sophisticated model like 42LM6690 and watch 3D movies to your heart’s content with stunning visuals. Take it from someone who already has and is using the Cinema 3D LED TV. Also 2D to 3D conversion is better with this TV than most others, I believe.