Do you mean head gasket or valve cover gasket? A leaking valve cover gasket will do what you're describing. A leaking head gasket, on the other hand, will cause overheating, mixing of engine oil and radiator coolant, constant steam from the exhaust pipe, and power loss. If you don't have these problems, you don't have a leaking head gasket.
As for replacing the valve cover gasket, aka tappet cover gasket, labour shouldn't cost more than Rs 1500. It's a one hour job at the most.