try audiworld.com forums for the C4  A6

My own reply.  I took it to a garage to have the bearing replaced.
The mech' said he had several problems getting nuts off etc.  The car
was up high on the lift so he had good access.  The garage also had
the pullers and press for doing the bearing.  When I saw the car up on
the lift and after hearing what the mech' said I was glad that I did
not attempt it myself on the ground using the jack and blocks, it took
a while to get the steering link nut off the knuckle as it kept
turning the whole unit.  The cost is going to be about £190.  If the
hub had been damaged then another £80 could be needed.  The hub
bearing kit that the garage got included replacement nuts and bolts.
I took the car there for 0900, at 11.30 the mech said there was about
1/2 hrs work left plus a road test.  I said I could call back in a
couple of hours and collected the car at 14.00.  They gave me a price
for doing the bearing before I took it in, which was about £180 +
vat.  However there was some confusion as to the price as the
condition of the hub was not known.  They got a hub as well which they
could rtn if not used.