The correct way GM lists in their service manual is to take off the engine dog bones, attach a pulling strap to the engine and hoist and roll it until you gain access. That is the same procedure for many SUV/Van GM front wheel drives.
Pass side closest to fire wall below alt.
Written under the hood on a placard and in your owner's manual.
On the '04 is .060 inches or 1.52 mm. Not sure if it's the same for every year.
If there is it will need to be flashed by buick to activate the plug
Mark them first with a marker and change one at a time
The spark plug gap for a 2003 Buick LeSabre should be set at .060 inches. The best spark plug for this vehicle would be an Iridium plug.
2000 Buick century gap for spark plug 3.1l
The spark plug gap setting on a 1994 Buick Century is .055 inches. A new spark plug will come preset from the factory and should not need adjusting.
The Spark Plug Gap.060 (In thousandths of an inch)
Remove the spark plugs wire and remove the plugs wit a spaerk plug wrench or socket.
Disconnect the battery, remove the boot cover and spark plug cables, and pull out the old spark plugs. Put in the new spark plugs, replace the boot cover, and spark plug cables, and reconnect the battery.
Spark plug diagram for '98 buck regal