Gov. Jim Gibbons urged the Justice Department on Friday to carefully examine the pending merger of United Health and Sierra Health Services before allowing it to go through.The merger has already been approved by Nevada Insurance Commissioner Alice Molasky Arman.He said the similar merger of PacifiCare and United Health two years ago produced nearly 133,000 violations of state law and regulations "as well as many improper claim denials.""Far too many Californians were negatively affected by the PacifiCare and United Health merger, costing both consumers and physicians millions of dollars out of their own pockets," he said his letter. "These staggering …