"Rich history" might not be the first phrase that comes to mind when looking at a seventh-generation Buick LeSabre, but there's plenty of heritage there if you peer a bit deeper. The LeSabre nameplate itself dates back to one of the most celebrated and radical concepts of its day: the Harley Earl-designed 1951 LeSabre concept car. While following iterations of the LeSabre might not have been as seminal as the original LeSabre concept, the "Fireball" V-6 introduced in 1962 certainly was. Based on a Buick-designed, all-aluminum V-8 -- later sold to British Rover, which used it for the next 50 years -- the 3.8-liter Buick V-6 eventually went on to power the awesome Grand National, and to influence the design of practically every purpose-built, American V-6 produced since then.
Find a belt-routing diagram sticker under the hood. If you can't find one, then draw a routing diagram with a pen and paper, and take a few reference photos with your phone.
Slip a socket or the box-end of a wrench over the bolt in the center of the tensioner pulley.
Pull the ratchet or wrench counterclockwise to relieve tension on the belt, then slip the belt off the engine. If you have trouble routing the belt under the bottom pulleys and keeping it centered, you may find it easier to remove the wheel and wheel-house liner, and have an assistant hold the bottom of the belt while you route the top.
Hold the belt tensioner with the wrench while you slide the belt over the pulleys and ensure that it's centered and seated in the pulley grooves. Turn the ignition key to "bump" the starter a few times. Inspect the belt to make sure it's still straight and seated, start the engine and inspect it again.
