Coolant

Have to make sure have a good battery and starter is good too
Check if have coolant in cylinders and to do so remove spark plugs
check if have coolant and oil mixed and if so oil will look like very thick milk shake
if have oil and coolant mixed or coolant in the cylinders its a head or headgasket
if not check starting system and pressure check coolant system for leaks

If you have run out of coolant the engine may be seized, you will have to remove the plugs and try turning the engine over by hand, if it won't turn it will be seized, as for cost, this is to hard to say without knowing the extent of the damage.

Mark (mhpautos)