generally, how expensive is it to fix codes P0128, P442 and P456 in a kia rio 2001?

Question

I have a 2001--Kia Rio with codes P0128--coolant thermostat malfunction, P0456 Emissions, very small leak, and P0442 - emissions leak-small.

Fuel cap passed
DLC passed
KOEO passed

This is greek to me.

Thanks!!

Ruth