How did the CIA attempt to protect oil interests and prevent the spread of communism in the Middle East?

The CIA doesn't do that stuff. They'd help with the first through third, but they aren't an entire military or political organization. In terms of other countries they get information to protect the US and its allies, have agents go along with special operations like Delta Force or DEVGRU (SEAL Team 6), and keep an eye on enemy. More than that and it gets trickier... They might fund certain people or cut certain things but it'd be difficult and way too intricate to put a shah in power. Remember it's an *intelligence* agency... Not some kind of illuminati.