If it's a frozen fuel-line have the AAA tow you 100 miles and park you in a garage. In about a half-hour you can dirve away.
To the gas station.
Really though, the idea of putting some gas in it is a very good place to start.
The loss of interior heat is more of a concern to me.
If your thermostat stuck then your engine has been overheating. It may have heated enough to have boiled away the engine's coolant. No water to heat, no heater.
You have to take it out to change it. You can check it after you take it out by putting it in a pan of water on the stove with a thermometer in it. It should visabley move once the temperature reaches 180 to 195 degrees. If it does it's good. But buy one anyway. If you have my luck it will go bad a couple of weeks after you've put it back in. The cost is less than $15 for most vehicles.
It's even worse or at least equally bad if something is leaking as Arch said. If there's ice on the floor of the passenger side, (you said it's 4 degrees outside), then your heater core is leaking. Otherwise look for tell-tale signs of water leakage aroung the hoses and at the water pump.
As cold as it is there there may be an ice trail from the leak or signs of a stain where water has been leaking out and getting burned off the engine leaving behind a trace of minerals and burned anti-freeze.
In addition, pull the dipstick and look for water in the oil. It will look creamy-colored and foamy. That will happen if a gasket is bad. Overheating an engine a lot can make a gasket go bad. On the other hand, a bad gasket leak can cause the engine to lose coolant and overheat. Kinda like the chicken or the egg thing, only this one can be figured out without hurtin your head. Unless you bump it on the hood. Now that really hurts. The edge of the hood is sharp. So don't do that.
Either way, driving around with a very low coolant level has the possibility of severely damaging your engine if it hasn't already. When engines severely overheat they just shut down with a few jerks like the muscle spasams of a dying fish out of water.
Both of them, fish and engines, need water.
It could however be as simple as a loss of vaccuum at a hose which controls the valve that allows the hot water to enter your heater core, which in turn allows your heater fan to blow the hot air off the heater core.
Find the water hoses that are connected to your firewall and trace them back toward the front of the car until you stumble upon something that looks mechanical, looks as though it may be in line with the water flow from your engine into the firewall and also looks like it could be the valve that I talked about ealier. See if there's a small black hose attached to it. Look to see if that hose is broken, cracked or unattached to the valve.
If it's cracked replace it. If it looks to have broken-off where it should be attached, replace it. If it's simply slipped-off than plug it back on. If it looks good you can check it once the engine is running again by taking it off of the valve thing and holding your finger over the opening. You should feel it sucking if you tap your finger on and off the end of it. If it does then it's probably ok. But still might not be. You can take that to the bank.
It could also be that your fan quit working and can't blow heat off the core no matter how hot it is. They're not expensive or hard to change. You can check it by turning the fan on and listining for it either from in the car or out of it. If it isn't making any noise it isn't working. But you knew that.
Put some gas in it and check out the possibilities of a stuck thermostat, a leak, a leaking vaccuum hose or a faulty heater fan.
Of course, none of this means that any of this is your actual problem. You didn't give much detail as to exactly what happened. I was just trying to give you some ideas since you said you knew nothing about cars.
Am I a mechanic?
No, but I did stay at a Holiday Inn Express last night.
