Yep, guessing rather than not diagnosing, and not familiar with subarus.
I could be wrong that it’s the center diff…but I’m not. Haha.
Dealer is a great option, another good call on your part. They’ve got this job down, probably have the part and gasket in stock, will use the correct fluid, there isn’t much else job-specific to go wrong or get uncharged for on this job (still might upsell a brake fluid change or something else!), cost will be reasonable (high end but reasonable) and they will know it’s the VLSD as well so that’s a nice triple check (you - usmb - dealership) before going through with it.
I’m generally picky about when and how to use a dealer and this is the perfect job and situation to let a dealership handle.