An obscure Central Contra Costa County public health district with no hospital, declining tax revenue and rising costs is trying to avert extermination. With a dissolution vote likely to take place early next year, the embattled Mt. Diablo Health Care District has in the past two months retained an attorney, handed out tens of thousands of dollars in grants and voted to hire its first-ever general manager. "It's like the phoenix rising," said Grace Ellis, district president and a 23-year veteran of the board. "The health district is alive and well." However, the district's attempt to transform itself into an indispensable public service and avoid elimination has angered critics.