Q1 some work shops may try to help you out ware they can, depending on what your after. Most have set rates and charge accordingly, although I am sure it cost the same to change a tyre on a AMG as it does a Falcon but the price may vary a bit from place to place
Q2 as for the clunking it may just be the new clutch is making it a bit smoother on the change. normally diff chatter on AUs (
irs) can be quieten down with the correct oil and additive