There have been two generations of the Yukon XL. The first generatoin was made from 2000 until 2006. The engines on those models ranged from a 5.3L Vortec V8 to a 8.1L Vortec V8. All models came as four speed automatics.
For the 2007 model year, General Motors introduced the GMT900 platform for the redesigned Chevrolet Suburbans and GMC Yukon XLs.
These vehicles were on dealer lots by April, and they featured a modernized look with aerodynamic exterior styling. The interior was redesigned as well, with leather seats and 9 passenger seating (also available on the previous GMT800 models) options.
These SUVs are prized for their towing capability, which is greater than any other full size SUV on the market. They can tow up to 9,700 on the 3/4 ton models, making them a favorite among campers and boaters alike.
Since these SUVs are typically bought by people who can afford to lease them for a couple years and then get a new one, there are plenty of used Yukon XLs on the market. If you can't find one in your local classifieds, check on eBay. There are also a bunch of parts and other crap on there, and an ever-growing aftermarket and modding community.