After first service, Tata recommends changing engine oil after every 10000kms, however if you are not using synthetic and company recommended engine oil than the frequency of the change will be different. Brake oil and coolant need to be changed after 40,000kms, however it can be necessary before the described schedule as well, which depends on the usage. Transaxle oil need to be changed after every 20,000 kms.
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.