What is price for installation? One shop said $6000 with tune, which I thought was a bit much. Others won't tell me a price unless they have part numbers and the specs of the cam.

$6000 to install and tune Alloytec/SIDI cams is too much. Generally, the installation of these cams would be around the $600-$1200 mark, while a custom tune to suit your VZ Commodore would be between $800-$1200.