Supervisor Mark Ridley-Thomas will mark his 100th day in office Tuesday by outlining his vision for reopening Martin Luther King Jr.-Harbor Hospital, which was the central point of the campaign for his seat and remains one of the most pressing issues facing South Los Angeles.

Ridley-Thomas said last week that King-Harbor is on track to be reopened as a 120-bed facility in 2011, possibly 2010. Though he has yet to disclose details about his strategy to get there, he is among the county officials who have suggested reopening the hospital in stages, ramping up to its previous capacity of about 400 beds.

Shortly after taking over the 2nd District post from retiring Supervisor Yvonne Burke, Ridley-Thomas called for a report from county staff on cost estimates and a timeline for a seismic retrofit of the facility as a first step toward that goal.

The report, which has been subjected to more than a month of delays, is due back to the board March 17. It puts the price tag for the renovations at about $200 million, Ridley-Thomas said.

It is still being decided how many structures on the campus can be saved versus how may will have to be rebuilt outright, Ridley-Thomas said, adding that the goal was to save as much as possible.

“The whole idea was to engage in what we think will be rather significant cost savings, rather than the demolition of the current hospital’’ by taking advantage of existing structures, Ridley-Thomas said.

Another key hurdle in reopening the hospital will be finding an organization to run the facility, which Ridley-Thomas was expected to discuss Tuesday. County officials are attempting to convince the University of California system to take on the task, and an update on their progress was expected by March 17.

In his bid to represent the 2nd District, which includes parts of South Los Angeles, Compton, Culver City and Inglewood, Ridley-Thomas squared off against Los Angeles City Councilman Bernard Parks in a progressively bitter election.

Most of the county supervisors, including Burke, threw their support behind Parks. Supervisor Gloria Molina was the most outspoken in her support of Parks, or rather, in her denouncement of Ridley-Thomas.

Ridley-Thomas received millions of dollars in campaign funds from the county’s powerful unions, which Molina said would prejudice his decisions.

So far, however, that has not been a problem, she said.

“It has been very good and we have not seen any issues,’’ she said.

But Molina noted that relationships between unions and the county over the past 100 days have been good, and that Ridley-Thomas’s strong union ties could be more apparent during future contract negotiations.

“That’s when we may see it,’’ she said.

Co-workers — including Molina — gave Ridley-Thomas high marks for his work so far, not betraying any traces of the contentious nature of the election.

“It has been very refreshing and quite enjoyable,’’ Molina said of working with Ridley-Thomas.

When asked if he seemed to have held a grudge for her backing of Parks, Molina replied, “Surprisingly not, considering that I was a very pro-Parks individual.’’

County CEO William Fujioka praised Ridley-Thomas’s work ethic and commitment.

“I tend to work a long day, but I see his car when I get in and it’s there when I go home,’’ Fujioka said.

In a written statement, Supervisor Michael Antonovich said Ridley-Thomas “has proven himself to be proactive and engaged in the issues affecting his constituents and the county. ... He is committed to the resurgence of Martin Luther King Hospital and providing quality medical care to the community ... ‘’

Supervisor Don Knabe said the experience of being on the board was an eye-opening one for Ridley-Thomas, who resigned his post in the state Senate to assume his supervisorial duties.

“In the beginning he was a bit overwhelmed by what we have to do here,’’ Knabe said. “It’s not like the Senate. You don’t get to have a lot of discussions about esoteric things. We have to fix problems.’’

One of the delicate issues Ridley-Thomas had to handle in his campaign was how to sell voters on the idea that he was the savior who would reopen King- Drew, without alienating the other supervisors who have struggled to reopen the hospital since its closure in August 2007.

In particular, he avoided publicly blaming Burke, who had overseen the 2nd District during the hospital’s decline and closure, but who was still a hugely popular figure.

Ridley-Thomas pledged to bring a “laser-like focus’’ to the problem.

Knabe suggested that because Ridley-Thomas hadn’t been privy to all of the board’s behind-the-scenes discussions until he was elected, he may not have understood how hard the board was already working to tackle the problem.

“We had not been sitting on our rear ends. We had been working diligently,’’ he said, adding that “Yvonne, she was plenty focused on MLK. But she took a lot of heat from the community.’’

Either way, Ridley-Thomas has clearly made the issue a top priority, hiring a team of three health deputies instead of the usual one, and hiring high-profile health care advocate Sylvia Drew Ivie to be his chief of staff.

“Health is really a big priority for him,’’ Drew Ivie said.

One hundred days in, Ridley-Thomas is still in the process of fleshing out his staff and adjusting to his new offices.

Drew Ivie estimated that about two-thirds of the staff were in place, with the justice deputy and human services deputy positions still notably unfilled.

Several of the old guard from Burke’s days will remain, including Karly Katona, who has been named environmental deputy — a new position.

Katona will take on issues such as the revitalization of Compton Creek.

“We have a big agenda and a lot of good people, so we’re excited,’’ Drew Ivie said.