First off, are you reading the hydro date correctly? this thread explains them very well
http://www.pbnation.com/showthread.php?t=2059688
If the hydro is truly overdue, empty it and ship it out for a hydrotest. While the quick answer is yes this is something you don't want to mess with or take a chance. The sheer energy stored inside that tank can send it through a wall and kill anyone in the next room.
also, do not fill from there anymore. If they can't take the time to ensure the safety of your tank that calls into question the safety of their own equipment.