ADN by Sean Cockerham.  Sean Parnell (NGP Photo) on Tuesday begins his first legislative session as Alaska’s elected governor, freed from his caretaker status as Sarah Palin’s (NGP Photo) replacement. He’ll try to lower the oil tax championed by Palin and push forward on the multibillion-dollar Susitna dam.  Parnell comes into the three-month legislative session enjoying a state budget reserve of about $10 billion, the envy of cash-strapped states around the nation. Big money from high oil prices and the oil tax have flowed to the state even as North Slope crude production continues the decline that began after 1988.