Kevin Kelly supplied the photos below to show how easy it is to change the transfer case fluid on a 1989-1995 Classic and 1995-2002 P38 that all have the Borg-Warner auto locking transfer case.  All Range Rovers with the Borg-Warner transfer case use Dextron III automatic transmission "fluid" (ATF).  (Range Rovers built before 1989 with the manual locking transfer case use traditional gear "oil").  It is important to use "Dextron III" ATF in the transfer case.  The manuals for all Range Rover Classics will call for "Dextron II" since the almost identical, but slightly improved Dextron III came out just about the time the last Range Rover Classic was produced in 1995.  Dextron II has not been produced since Dextron III was introduced.

Kevin reports that all you need to get is an inexpensive pump that screws in to the ATF bottles to pump it in and a 1/2" breaker bar with an extension.You don't need a socket since just like the fill and drain plugs on the RR Classic and P38 front and rear differentials  the fill and drain plugs on the transfer cases are 1/2" square so the square socket extender end fits right in to both the fill and drain plugs.After using the pump store it in a zip lock bag so it won't leak all over the place.
 

Removing the fill plug from the transfer case	Inexpensive oil pump that screws into plastic ATF bottle

Use Permatex Halomar on the threads for the plugs to stop weeping.  Another tip is to always remove the "fill" hole plug first so you won't drain the transfer case and then figure out that the fill hole is stuck so you can't drive the vehicle!!
 

Removed plugs  and a tube of Hylomar