Christian Ehrhoff had a career-best three assists and Evgeni Nabokov made 24 saves for the Sharks, who shook off a sluggish start in their return from a lengthy road trip to win their fourth straight home game - their seventh victory in nine games overall.
The Sharks broke it open when Guerin capitalized on a remarkable centring pass from Ehrhoff early in the third period. Guerin, acquired in a trade with St. Louis last month, buried his eighth goal in eight games after failing to find the net in his first six games with the Sharks.
Brian Willsie scored and Sean Burke stopped 23 shots for the Kings, who lost to San Jose for the fifth time in seven meetings this season.
San Jose is tied with Dallas and Minnesota with 98 points in fifth place in the Western Conference standings. The Stars and the Wild also clinched post-season spots Tuesday.
Joe Thornton's 10-game scoring streak ended, but the Sharks thrived with three points from Marleau and another solid effort from Nabokov. The goalie was pulled from his last start at Carolina, but hasn't lost in regulation since March 2.
The Sharks won twice and lost in overtime during their four-game road trip, keeping pace in the conference race, but not excelling enough to threaten Anaheim atop the Pacific Division. Five of San Jose's final six games are at home, including Sunday's second visit from the Kings in six days.
Marleau scored his 31st goal of the season on a power play midway through the first period, rifling a long rebound over Burke's far shoulder. Los Angeles surged in the second period, and Willsie tied it with a quick power-play goal against the Sharks' slow-to-react penalty killers.
San Jose took the lead during 4-on-4 action thanks to an alert play by Ehrhoff, who also assisted on Marleau's goal. The defenceman stretched out to chip the puck from the boards all the way to Guerin in the slot. The veteran forward buried the chance for his 36th goal of the season.
Marleau then slipped behind the defence for a breakaway with 10 minutes left, capping the 23rd multi-goal game of the San Jose captain's career.
The Kings found a ray of hope in another gloomy season earlier Tuesday when they signed college defenceman Jack Johnson, the third overall pick in the 2005 draft. Johnson, acquired from Carolina in a trade last September, is expected to play for the Kings at home Thursday night against Vancouver.
Notes: Kings D Lubomir Visnovsky missed his third straight game with an ankle injury, and Derek Armstrong missed his ninth game with a knee injury. ... Before the game, the Sharks held a brief ceremony honouring coach Ron Wilson, who coached his 1,000th NHL game during the road trip. The team presented Wilson with several gifts, including the framed original scoresheets from his first and 1,000th games. ... Sharks D Scott Hannan sat out with an undisclosed injury.