If your car is running fine then I can't understand why you should need replacement valves and cylinder head. T
The engine is basically made of cast-iron and if the coolant has never been drained and renewed there will of course be rust, and a build up of sludge. This could well have blocked the the heater matrix and caused the heater not to function. It could have blocked your radiator too but you didn't say that your car engine has overheated. It may well be that the heater matrix is too far gone, and also that a blocked radiator is impeding water circulation and thus require replacement. It is worth checking the water pump function too. If coolant renewal is included in regular servicing then these corrosion related issues don't happen so often.
What other symptoms led them to believe that the valves and cylinder head need to be replaced? Has the car not been serviced regularly and perhaps have overheated?
ChicksFan
November 2012