The heating not working is a sign of the car losing water. the heater matrix is at the top of the cooling system and so as the level drops there is no water to conduct the heat to the inside of the car, it's one of the first things you notice when you lose water.
The loss could be due to somthing simple like a burst radiator or pipe but could also be as a result of a blown head gasket, cracked head or even a cracked block.
It sounds like you have also overheated the engine and caused other damage.
Unles you are able to do it yourself (which sounds unlikley or you wouldn't have posted on here) then it will probably be cheaper to replace a car of that age, than pay a garage for a rebuild or fit an other engine. But get an expeienced mechanic to have a look at it first just to confirm the extent of the damage. You might be lucky.