WARNING: This page is about a different car, the 2006 Buick LaCrosse and 2006 Buick Allure. However, it is still accessible from the selected car via links, so may be relevant.
Fig 1: Oil Level Indicator
Courtesy of GENERAL MOTORS CORP.
Remove the oil level indicator.
Loosen the nut holding the oil level indicator tube bracket to the exhaust manifold stud.