Hey Neha, 2 nights 3 days will be good to cover all the places in Ooty. You can take a bus from Chennai to Ooty. Here's a list of places you can cover in Ooty.
Hello..I'm a native of Ooty..you need atleast 4 days to visit all the beautiful sight seeing places like, needle hill ( Gudalur), emarald dam ( interior places in Ooty with lakes and mountains), and other places ..