Former Bayern Munich striker Guerrero netted for the Copa Libertadores champion to secure it a place in Sunday's showpiece fixture in Yokohama at the expense of El-Abry's side.
The Brazilian side took a deserved 1-0 lead when Guerrero headed Douglas' inch-perfect cross past the Al-Ahly goalkeeper Sherif Ekramy in the first half, and despite the African opponent improving after the break an equalizing goal never materialized.
Corinthians, making its first appearance in the tournament since winning the inaugural edition 12 years ago, had a reported 20,000 fans in the stadium and it certainly sounded like an accurate figure as Timao's supporters urged them on from kickoff.
It was the Copa Libertadores champion that fashioned the first shooting opportunity of the match, with attacking midfielder Douglas flashing a half volley just wide from a difficult position outside the Al-Ahly penalty area.
That Douglas chance seemed to spark Al-Ahly into life, as after nearly going behind the club immediately went up the other end and threatened to break the deadlock. Ramy Rabia was the player who came close, as his header from a fine Walid Soliman cross from the right drifted off target.
Corinthians' first-half dominance finally paid off in the 30th minute when the Brazilians went 1-0 up through Guerrero. The former Bayern Munich forward headed Tite's side into the lead after connecting well with an audacious cross from the outside of the left boot of Douglas.
Mohamed Aboutrika's influence on the game after coming on as a substitute grew as the match wore on, but even with his probing play Al-Ahly failed to find an equalizer, as Corinthians held out for a narrow 1-0 victory.
Tite's team will now face the winner of the semifinal between Chelsea and Monterrey, with the final being held at the International Stadium in Yokohama on Dec. 16.