There are no special benifits and discounts for physically handicapped persons sir, Please contact your nearest dealer for the initial down payment and then emi options as well, they also help u in getting a loan or car finance. You can follow the site for know about the dealers in your city: http://www.cardekho.com/Tata/cardealers
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.