The car: 2000 E320 4Matic Wagon.

I'm considering purchase of this car. The dealer did have some service records, and the records indicate that the transfer case was replaced under warranty at 20,000 miles. The invoice seemed to indicate that the transmission was replaced along with it, but I couldn't tell with 100% certainty.

My question: on this vehicle, is the transfer case and transmission a single unit? Or could they be replaced independently of each other?

Thanks in advance.

Jonathan