If you buy it on Amazon.com , you will have to check if it will ship to India. Some products do and some don't. It will be mentioned on the web page or will come up sometime during the purchase procedure.
Assuming it can ship to India, as you reach the last page for purchase they will itemize the cost and show the shipping charge and 'advance customs duty' also. So you needn't worry about customs in India as it is handled by Amazon's authorised people here. The unit will be delivered to your door without any hassles from anyone.
However if you buy on Ebay or from some other company , they don't collect duty and you are at the mercy of the customs people. Clearance time and duty depends on which port the item enters. Kolkata and Chennai seem to be particularly nasty people ! Delays of up to 1 month is normal and duty can sometimes be zero and sometimes 100% or more ! You have to then send it back for re-evaluation with documents proving the price and how much you paid ( credit card email ) etc.
Amazon is best ! No hassles .