There is no engine block drain on a 2005 Buick LeSabre
Here is the radiator drain.
Cooling System Draining and Filling
Caution: To avoid being burned, do not remove the radiator cap or surge tank cap while the engine is hot. The cooling system will release scalding fluid and steam under pressure if radiator cap or surge tank cap is removed while the engine and radiator are still hot.
Important: Draining the cooling system with the pressure cap installed will syphon the coolant from the overflow tank.
Notice: The procedure below must be followed. Improper coolant level could result in a low or high coolant level condition, causing engine damage.
Important: Use a 50/50 mixture of DEX-COOL antifreeze and clean, drinkable water.