H1 B Extension and Ammendment from India

Hello Team,

Currently i have my H1 B Petition and Visa is valid till March 13 2017. My petition is approved for X client in Texas and i want to travel to Y client in NJ. can i file for extension and ammendment together now. can i travel to new Location as soon as i file extension and ammendment or do i need to wait for the complete decision. what will happen if my visa is expired in the process. please clarify my Query.