Thanks for all replies.. I did my ATF change last week.

To sum it up
1) Drain screw size is 24mm. Need a socket wrench for this (I was using the ratcheting type)
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2) The drain screw is located at inconvenience place - just above the lower arm on the left side (@MR_alien did mention about this). Without proper guttering, the old ATF will spill all over the place.
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I improvised a plastic bottle as a gutter
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3) Almost 5 litres (5 bottles) of SPIII ATF needed for replacement (mentioned by @erictioh). 4.5 bottles of ATF just barely above the HOT mark at 'N'. Refilling ATF is easy - just need to put funnel and pour the ATF in (no need extended funnel)
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