It is 8 quarts not 6, cwdilg is right.

As for the time interval, I believe the recommended interval is 12 months with the 0w40 synthetic, but there are factors such as temperature as well.

The car has an oil change indicator, it will come on when you need to change your oil.

You should almost certainly not follow the same service schedule as your Sebring, the Sebring isn't designed to use 0w40, not all engines and oils are created equal.