MacBook late 2008 13inch SSD, and OS X question

Hello, I will be getting my first MacBook in a couple of weeks and wanted to do some upgrades. First of all, I want to put in a Solid State Drive. I know which one to get, but if I install it, will the OS X be on the hard drive or will I have to do something else. Also, I want to have the latest version of OS X on it (El Capitan) but the version that its coming with does not have an app store. Does that mean that I will have to purchase a copy of Snow Leopard and then upgrade it from there? Lastly, the track pad (mouse area) won't click. I'm guessing its from a bulging battery? I've read a lot about that being a problem. I'm wondering where I should buy the battery as I have gotten lots of different prices on the internet. I'm hoping that is the fix but if y'all have any other suggestions, then please let me know. Thanks!