99' Venture with NO heat..need help

My 99' Venture has been one nightmare after another! My most pressing problem is that my heater cut out about three days ago. The air blowing in is cold and the higher I turn the the blower the colder the air seems to be. We've recently replaced the water pump, pulley system, serpentine belt, engine (used and worse than last one it turns out), blower motor, starter (or alternator can't remember which), battery...the list goes on. My temperature gauge rises if the car idles, and the coolant light goes on and off, Pep Boys says my gaskets & hoses are leaking, my "new" engine may be cracked and the whole thing needs to be replaced again....I know we won't have it much longer but it is the only car I have and I do not have anything to replace it with...what can I do to get the heat back or supplement it so my kids and I aren't freezing this winter? Also, the mechanic that replaced the engined warrentied it for a year and then split, I can't find him anywhere, do I have any recourse with out knowing where he is?

it takes water and coolant to make heat . in other words the radiator has to be full and the cooling system can't have a big leak . a drip in a hose and you can get by with. but if the cooling system can't hold the water/coolant mixture long enough to make heat then the big leak has to be stopped.what does the temp gauge do? stay at one place a little then gradually move or does it move up and down erratic? an erratic temp gauge usually means a blown intake gasket. it takes a little while to empty the resivoir then the radiator. a cracked head or head gasket it usually tries to run hot.are you sure there is a thermastat in it?or it could be stuck open.as far as the mechanic warranting the engine for a year . go to small claims court and make out papers and let the legal system track him down.call the bbb in your state and make a complaint.in other words put the heat on him