My 2001 Passat has sat in a yard for a year. In June the battery statrted to die. The person watching my car let my battery die all ogther and it will not hold a charge. How do I replace the battery and what tools do I need?

Tools; Mainly a 10mm socket, ratchet and extension. Remove the top battery cover by pulling straight up. Use the 10mm socket to loosen the nuts on the + and - battery terminal connectors. Wiggle the connectors back and forth and pull them off the battery. Look around the bottom of the battery box, there may be a plastic wedge with a bolt thru it clamping the battery down. If so, remove it with the ratchet and extension. Drop your new battery in and reverse the procedure. Now the worse problem, your car will probably need to have a throttle adaptation performed if it is a gas burner or it will run rough until it "relearns" the proper settings.