I believe the date of that GM Bulletin was 3-5-2004 so it is nothing new.
Myself, I plan to check the K&N Aircharger filter every year and clean it if I think that it needs cleaning and then spray the air filter lightly with air filter oil. If not I will check again the following year by cleaning and oiling.
Generally there should not be any need to clean and oil this filter regularly but K&N suggests to inspect once every year and then the K&N Aircharger instructions states to service filter every 50,000/100,000 miles. Sooner under extreme dusty conditions. To service: Soak in K&N filter cleaner, rinse with water, dry completely (do not use compressed air), re-oil with K&N Filter Oil. Myself I will use the aerosol oil spray as I can limit the amount of oil that I put on the filter better then squeezing oil out of a squeeze bottle along each pleat. They suggest letting the air filter set for 20 minutes before reinstalling on the vehicle. Myself, I will let it sit overnight then install the filter the next day.