[Richard]

They can be removed without letting air out of the system. They are usually a BEAR to remove. If the big filter wrench slips, clean the cannister with a solvent to remove the grease. Wrap it with self sealing pipe repair tape (Lowes) which is super sticky. It will cling to the cannister, and give the wrench something to grip.

Grunt !

Please, crib underneath the coach at a hard chassis point. You'll be in a tight place and you don't want the coach to squeeze you and ruin your day. You'll find a great point right behind the tag mud flap just before the engine cradle starts to use as a hard chassis support.