Hello Mr. Singh,
Tata Motors hasn't made any official announcement regarding the launch of Tata Nano Diesel, as of now. However, it is being speculated that it would be launched in India by mid 2014. Stay tuned to Cardekho for more updates on the same.
New Tata Nano with EasyShift is available at Rs. 2 lac (Ex-showroom, Delhi), and the final cost depends on the valuation of your car. So, first get the valuation of your car from authorized Tata dealer, so he can give you a final quote for the new car.