Leaking heater core
The coolant is old, broke down, and needs replaced.
Sounds like your heater core has a leak and the sweet smell is your coolant.
Low coolant level? Thermostat opening too soon? Plugged or restricted heater core? Water pump not circulating coolant? System airbound?
The heater core is leaking coolant.
High pressure coolant is blowing out through a small hole in your heater core, it will need to be repaired or replaced. If it is warm out it might be AC refrigerant leaking.
You would have a leak in the coolant system somewhere and you need to have the system pressure checked.............
One could possibly find diagrams for 1997 Jeep Wranglers at a Jeep Wrangler official site or through a manual company. Another good idea would be to just consult a mechanic.
The smoke you see may be moisture/steam. The heater core is probably leaking engine coolant. If the "smoke" has a sweet smell to it, it's engine coolant. More info about the vehicle such as model and year would help.
If we are talking rain water not engine coolant I would suspect the drains under the cowl are plugged up with debris (leaves and such). If it is engine coolant then I would suspect the heater core is leaking.
the reason that the heat would cease to work when the car overheats is that the car is low on coolant. coolant is warmed by the engine as it transfers heat away from the engine. the heated coolant passes through heater hose and through the heater core. The blower motor blows air through the heater core warming the air and pushes the warm air through the vents in the car to you. the heater core is a small radiator in the dashboard of most vehicles. If there isn't coolant in the car, the engine becomes too hot thus the overheating. a side effect of this is that the lack of coolant means that coolant cannot get to the heater core to be warmed to warm you
The "antifreeze smell out the AC vents" would mean only one thing, you have a small leak in the heater core.
your heater core element needs replaced. expect a heavy repair bill $150 - $200. They would have to pull your dash board off to get to it...