help with re-installation

Something happened with my Keychain Access (which isnt a huge deal, but is annoying) when I updated to Mavericks and I've just recently found out I don't know my root password. I need to do some work with sudo for my COSC classes, so I need it.

When we bought our MacBook Pro (mid 2012) from best buy we had the geek squad transfer my wife's files from here toshiba lap top. I regret it now cuz from what I've heard, installing mac osx is pretty simple stuff.

Anyway, I called the geek squad they said that they dont set root passwords, I've tried any and every password that we can think of, so i can only guess that the root passwd is the password from her toshiba laptop. In the system memory, it looks like the Macintosh HD is mounted on the "...Toshiba..." somehow. Or vice versa. We have no idea what that password is, So i think we are screwed there. I also have no idea why its mounted on there?

So I figure re-installing Mac OSx is my best bet--this should also reinstall keycahin-- . I dont have an install disc, my macbook pro come pre-installed. Do you normally get one with a macbook Pro? Can I download a file to boot from USB? Would I be able to update to Mountain Lion/Mavericks for free still?

I have everything backed up on my Time Capsule so I should be ok there. Are there any precautions I should take first.

tldr;

1. Where do I get Mac OS X install files for USB to re-install Mac OS X on my MacBookPro (mid 2012)?

2. Is it similar to installing other OS's? ie hit F12 during boot to choose USB file to boot from?

3. What precautions should I take when re-installing? Is it easy to do restore all my files with Time Capsule? ( It should be, I paid a lot of money for that!! )

4. Is there any way to unistall/re-install Keychain Access?