If I call them out:

1) Will it cost anything?

2) Do they check only for gas leaks (not CO)?

3) If it's a specific appliance, do they red tag and shut down the
appliance only (they've all got their own gas valves) or do they kill
gas to the whole house? I could get by without gas for a day or two.

4) Is there anyone I can call out to test for CO production from
appliances (if the gas company doesn't do it)?