For the availability of spare parts, we would suggest you walk into the nearest service centres. You can click on the following link to see the details of the nearest service centres and selecting your city accordingly - Service centre. Moreover, for an idea of the prices of the spare parts, you may follow the below link - Spare Parts.
As of now, the brand has not officially announced the but it is expected that the Skoda Rapid will get a brand new BS6 1.0-litre turbocharged petrol motor engine that is BS6 compliant rated at 115P/200Nm state of tune. There will no diesel engine as Skoda Auto Volkswagen India will not offer diesel engines in the BS6 era.