Marcus Tavernier had given Bournemouth a first-half lead, and new Cherries boss Marco Rose came within minutes of a dream away-day victory before Guehi headed Manchester City level in the 84th minute and Gvardiol converted a Rayan Cherki cutback deep into stoppage time to complete the turnaround.
Guehi, deployed in an unfamiliar midfield role, told BBC Match of the Day the result reflected City's resilience.
"We did well. There was a lot of chances we created early on before they even got the first goal. After, I feel like it was a good reaction. I'm super proud of everyone and proud of the fans for sticking with us. That's the spirit we need to have every single game, right until the end until the ref blows his whistle."
Asked whether he had played in midfield before, Guehi admitted it was new territory.
"Not often. But I enjoyed it today. I enjoyed it simply because I got so much help from so many people."
On missing one earlier header before scoring the equaliser, he added: "That's life. Sometimes it's really good, sometimes it's not really good. When things don't go your way you have to just keep going."
Guehi also addressed the scrutiny surrounding City following a summer of major change.
"We play for Manchester City, there's always going to be scrutiny whether we win or lose. We understand there is a lot of change at the football club. A new manager, a lot of important players have left, a lot of new players are coming in. The most important thing is that we keep our standards high."
Asked where he might play next, he laughed off the question: "Who knows? Maybe up front. We'll see."
Maresca, in his first Premier League match in charge, felt City deserved the win despite a nervy finish.
"Happy first of all because we won the game. I think it was actually a game we deserved to win early because we controlled the game and we created chances. We conceded and it became more complicated but overall I think it was a game we completely deserved to win."
The Italian pointed to the number of players still adapting after a late pre-season.
"Today we had four or five players that arrived very late 10 days ago. For them it is still almost pre-season. Erling is one of them, Elliot, Marc Guehi, Nico O'Reilly. It's complicated for them but they have done a huge effort to help the team." He explained the thinking behind the positional gamble. "Sometimes you visualise things. I know Marc from Palace and I always thought he could play as a midfielder because he is very good."
On the club's transfer business, including the agreed deal for Ayyoub Bouaddi, Maresca kept his cards close.
"I will speak now with the club after the press conference."
Asked about further incomings, he added: "We will see, it's eight days to go. For sure something is going to happen."
Bournemouth boss Marco Rose felt his side had let the game slip having controlled long spells.
"It was getting harder. My feeling was that we really had the momentum in the second half. They started to play some long balls. They made some simple mistakes. The game became more open. But a game lasts not 80 minutes, it lasts 90 minutes. We need to defend this corner kick better and the second goal was just too passive."
Rose, whose side had been unbeaten in 18 league games under previous manager Andoni Iraola, was left to rue fine margins.
"I'm a competitor. We came here for the tenth time. We have a lot of things to improve, but at the end, it was quite unlucky to lose the game that way. We had two situations, one corner kick and one attacking where we defended too passive and that's why we lost the game."