How much does it cost to replace the turbo charge in my 1999 S70 AWD VOLVO

The heavy white smoke is most likely a head gasket issue, especially if it smells sweet. Does it and do you have to add coolant? How is your coolant level? Typically, turbos will blow very blue/gray smoke, because the oil gets by the bearing seals as the turbo bearing wear out.

Costs for parts only $645 - $800. Google various online parts stores.