Create the NPC in the database with all the details you want including the race, sex, and size. Be sure to give it the 'ABH' special attack flags, so that it's immune to melee, magic, and won't ever aggro. Make the name in the database as "Soandso's corpse".
Next, write up your quest script for the depop and whatever other conversation you want to happen. Add the following code.
Code:
sub EVENT_SPAWN {
quest::settimer(1,1);
}
sub EVENT_TIMER {
if($timer eq "1") {
$npc->SetAppearance(1);
quest::stoptimer(1);
}
}
If you already have code in the EVENT_SPAWN and EVENT_TIMER blocks, make sure to merge the code in rather than maintaining two separate blocks of the same type. This is the same sort of code that currently puts the Sleeper to sleep (laying down), it should give you a corpse well enough.