Had this exact maintenance overlooked on a previous car for way too long, by the time I noticed the humming it had already caused some gear wear that a simple oil change alone couldn't fully undo. Cheap preventive service compared to what a full differential rebuild would've cost.

Diff oil change and a vibration diagnosis are straightforward but only if the mechanic actually knows JKU axle and driveline quirks. A general garage will change the fluid fine but might completely miss what's causing the vibration.

Second opinion on a 9k quote saved you over 5k and got you a better result. Never accept a full replacement quote on a CVT until a specialist has ruled out a valve body rebuild or belt replacement first.