Is the oil drain plug on a 2003 mustang reverse thread or did people at Goodyear put back in with an impact wrench last time they changed oil?
The oil drain plug on a 2003 Mustang is not reverse threaded. It's a standard left-hand-tight (righty-tighty, lefty-loosey).
If it seems reverse-threaded, it's highly likely that someone cross-threaded it during installation, possibly with an impact wrench as you suspect. Over-tightening with an impact wrench is a common cause of this problem.
