OK ... I guess I'm basically answering my own questions, but perhaps this info will help others in taking on the task of changing their air filter. Having spent the better part of a Sunday afternoon, I have now learned the secrets of air filter changing. My 2000 390XL has a Cat engine with the air filter (AF) on the driver side. I would think that many of these comments are generic to any diesel. The process is actually quite straight forward. The hard part is access and getting leverage. You will do virtually all of the work hanging head first into the engine compartment. Not comfortable. Depending on how Airstream and Freightliner oriented the clamps, you might need to get on the ground to do some of the initial loosening. But you will reinstall and tighten these same clamps from above to make the job easier next time (?). Loosening the inlet end of the AF from the flex hose is easy. Loosening the exit end of the AF is harder. The key is to completely loosen the clamp holding the AF to the aluminum tube leading to the turbo. Once this clamp is loosened and slid up the tube clear of the AF, you can aggressively use a sturdy blade screwdrive to pry the old AF off of the tube. Installing the new AF onto the tube is harder, because it is hard to find a way to apply strong leverage to force the tube into the rubber neck of the AF. I sprayed both the tube and inside of the AF neck with silicon spray. Then I rigged up two small sized ratchet straps (one on each side of the AF tube ... as close as possible to 180 degrees apart) to pull the AF onto the tube. This rigging was not pretty and the geometry/attachment points will vary based on your particular unit and ratchet straps, but if you decide to try this yourself, I think you'll figure out your own feasible rigging arrangement. For me, the key was to use the ratchet straps as opposed to just trying to use muscle power .. which I think would not be adequate. And there is not enough access room to try to recruit a second pair of arms to help. If someone else has figured out another way to do this besides (beside taking it to a dealer?), I'd love to hear about it. One more small point: I had to remove/re-attach a bare copper grounding strap that connects the power transfer switch to the chassis to permit clearing the AF removal/replacement. This only took a few minutes and required only a screwdrive. My AF is a part number 114810003, Parker Racor, 9.8”x19”, which costs around $70. Knowing what I do now, the job would probably take about 3 to 4 hours to do again. You can do the math to decide if you want to try it.