Lenovo Y510P Upgrades

I'm going to be purchasing the Lenovo Y510P within the next week or so. It will come with 16GB ram, 4GB nvidia 755 (SLI), 1TB hd +24GB ssd, and an Intel 4700 core i7. Here is a link to the laptop
http://shop.lenovo.com/us/en/laptops/lenovo/y-series/y510p/

I'm curious about a couple things to do with the laptop and so that's why I'm here.

Firstly, is it worth it buying an internal ssd? I've never used one and I'd like to know what you guys at the community think. I'll be playing games on it, this laptop will be used to play League of Legends, Wolfenstein, Civilization, Crysis etc. How much faster will my games load? Will it affect the quality of a game or just the load time? If you do think it is worth it, what size does an ssd have to be in order to fit? Can you include some suggestions? Price range is negligible for now.

Secondly, I want to hear some feedback on overclocking. You see, it's 2.4GHz but I have been seeing other places like digital storm that overclock it for their customers. Is it possible for me to overclock my i7 at home without ruining the processor? If so, how much could I overclock it? If you guys have any links to youtube vids I would really be grateful to have some.

Lastly, is there anything else I should purchase with my laptop? Any accessories you would highly recommend? I've already found a sleeve, bag, mouse, mouse pad and cooling mat.

Thanks for all the help!