I too have a Cat C7 and have changed the air filter on two occasions. There is no removable filter cannister, you must replace the entire unit as one. It is a sealed unit. Take it loose from the inlet hose , remove hanger bolts and clamp on outlet. It is a little tough to get working alone but it can be done.
I purchased my first one from Cat dealer in Yuma for around 115.00, but my second one was purchased from a NAPA store for around 75.00
Save the part number in your log book so you can get one if you are on the road
One other thing, I change mine at 15000 miles and my flow indicator has never worked correctly. It shows a full tube after only 100 miles. There is a problem with the rubber tube to the intake manifold. I am not the only one that has had problems with this on the Crescendo.
Hope all this helps. Let me know if I can help you further.
2005 Crescendo triple, 2000 Blazer toad, Brake Buddy,DW,2 cats and lots of patience