I'm a newbie with some technical skills, but not a lot.
Should I be using MetaMask for added security?
What does MetaMask do for me, exactly?
Also, MetaMask seems to only work for Ethereum-based coins. Is there an extension like MetaMask available for the other coins?
Yes you should use Metamask as added security to avoid hacking. It is good to use if you are trading in a decentralize platform like EtherDelta. You can also use it for transferring tokens without compromising your private key.