v6 TDI quattro, rear differential input shaft bearing broken?

Hello!

I have an Audi A4 Avant TDI V6 (AKN) Quattro, manufactured in 6/99, with 97,700 km.

It is likely that the bearing in the rear axle differential, on the side where the driveshaft enters, is broken.

1. Who knows if, in this case, Audi will take over the repair (or possibly a new differential) under warranty?? (The service book is complete).

2. Has anyone perhaps already swapped this gearbox, and does anyone know how to demonstrate it, i.e., whether the entire differential needs to be disassembled?
or whether this unit can be replaced from the outside (on the cardan shaft side)?

Thank you very much for your help!!!

hd