2003 Pontiac Aztec no heat, temp gauge very hot

There is a small radiator called a heater core that coolant goes through to provide heat to the interior of the vehicle. Look for a puddle in the floorboard area and see if the anti-freeze smell could be coming from the vents. You definately have a leak that is causing a loss of coolant and a loss of pressure. The coolant sytem must have pressure to function correctly and of course it must have anti-freeze as well. Look for leaking hoses in the engine bay and/or puddles under the vehicle to help you find the leak. When it is cooled off, check the coolant level and top it off as you may need some coolant to even find the leak. It may be the heater core or a hose leading to the heater core which is more likely as the loss of fluid to the heater core would stop the heater from working.
Don't drive the vehicle if it gets into the red zone on the temperature gauge. This will cause very harmful engine damamge.