The former oil exec will have to make tough decisions as he becomes a foreign policy leader

Rex Tillerson is now officially President-elect Donald Trump's choice to be secretary of state.

Tillerson has worked for Exxon Mobil Corp. for about 40 years. That experience, experts say, is essential, as long as there's clear separation from Tillerson's ties to Exxon Mobil and other corporations.

​"The first thing Tillerson is going to have to do is divest himself of his Exxon stock," says Steve LeVine, Washington correspondent for Quartz and author of three books on oil and energy. "He's got over $100 million in Exxon shares. He also has a $70 million pension plan."

He says Tillerson must divest himself from Exxon Mobil completely. While Tillerson may show some resistance, LeVine says the Senate must insist.

If Tillerson does all this, there is a good chance that he will succeed in his new position.

"If someone is looking at Rex Tillerson as a greedy, one-dimensional individual who only knows oil, this is a serious misread of him," LeVine says.

LeVine believes Tillerson will be able to do a good job as long as he spends the time to familiarize himself with the nuances of foreign policy.

"When you rise to the top of one of the major oil companies, you are a person who is extremely smart," LeVine says. "In addition to that, you understand economics, deal-making, you know the world [and] you're well-read."