It is not advisable to replace a main PCB without the right equipment. There are some things that have to be recalibrated when the board is changed, like metering, focusing and shutter speeds, all the setup data for these will be stored on the board when the camera is first calibrated in the factory.
Canon is worldwide so I see no reason you can not buy whatever part you want. But trying to get it form CanonUSA may not be the best of ideas. Especially if you live in India. Why are you not seeking that info locally?
I agree the MB is not an amateur repair job. They are not plug-n-play.