Managers at Marin General Hospital said Tuesday that they expect to spend more than $500,000 this fall on a campaign to pass a $394 million general obligation bond to pay for a major rebuild of the hospital. "Marin General Hospital will be the primary funder of the campaign," said Jon Friedenberg, Marin General's chief fund and business development officer. "We're going to run a full-blown campaign with phone banking, precinct walking, direct mail, endorsements and everything. It will be robust." A headquarters for campaign workers has already been opened adjacent to the hospital at 575 Sir Francis Drake Blvd.