It all depends on what the installer is going to do. Are the rear window and windshield still in the car. Is he going to remove/reinstall those. If those are not in the car now, then I would say 8 hours for a professional is quite a bit more than needed.

After I did mine myself (a bit difficult the first time) I found a friend who had his Chevy Nova done for $145 and it was a great job. But he didn't have to remove glass.

More info needed to make a good response. But, check around.