Alive or dead, it stays enlarged for the duration of the spell.
Unless otherwise stated, a spell lasts for its duration.
The only rule that covers general spell duration is a small section on page 203 of the PHB:
A spell's duration is the length of time the spell persists. A duration can be expressed in rounds, minutes, hours, or even years. Some spells specify that their effects last until the spells are dispelled or destroyed.
And the rules that cover monster death aren't very extensive either. Page 7 of the Monster Manual says, under "Hit Points":
A monster usually dies or is destroyed when it drops to 0 hit points. For more on hit points, see the Player's Handbook.
And PHB page 198 says, under "Monsters and Death":
Most DMs have a monster die the instant it drops to 0 hit points, rather than having it fall unconscious and make death saving throws. Mighty villains and special nonplayer characters are common exceptions; the DM might have them fall unconscious and follow the same rules as player characters.
Other than that, there's no specific rule that says spell effects end on a creature when it dies, unless the creature is the one casting and the spell requires concentration (PHB, p. 203), so they should carry on (exceptions might be made at the DM's discretion).
Thus, the creature would stay enlarged for the full 1-minute duration of the spell, whether dead or alive, unless your concentration is broken.
In AFMBE, as in most traditional RPGs, character death means "that character is dead and that's it. The player can generate another character now if they want."
AFMBE, also like most RPGs, assume a somewhat realistic world so video gamey things like "and the new character gets the old character's gear" is not a thing. New characters don't remember things the old one does or get things they had, they're a new person who was out there in the world and has now come on the scene. The old character was a person in the fictional world, they're dead, so except for police inquest and burial that's the end of their direct participation in the story. (They might come back as a zombie, though that's technically a GM-controlled NPC - although it can be entertaining to let a player play their zombified corpse attacking their former friends to blow off some steam and give them something to do prior to new-character introduction time.)
The player of the dead character would generate a new character based on the rules. You as the GM could allow them extra advancement and/or gear beyond a normal base character if needed in your judgement. Then you would introduce the new character at a point that makes sense in your story, ideally in a way that allows the existing characters to take them into their circle without relying on "well the players know they're a new PC so they may as well suddenly be best friends with this guy they just met." This can be during the existing session, at the start of the next session, whatever works for your group. In the end, everything should seem like a progression of events that makes sense for real life (or at least a movie version thereof).
That's for campaign games - in one shot games, often once your character dies that's it, you chill and watch the others till they all die too.
Of course you can implement any alternative way of handling character death, but this is the core assumption of what death means that drives every trad RPG.
Best Answer
It all depends on what is available.
Firstly, lets just cover exactly when a PC actually dies:
Just because they reach 0 HP, doesn't necessarily mean they're dead.
Now, as for what happens afterwards: it all depends on your game, and the DM. For the most part, there are ways to bring back party members from death, and the Resurrection spell is one such way.
A Caster in the party can learn this, if they are of high enough level, or, you can likely quest for a healer to do so. That is, of course, if the DM allows it. Talk to them to discuss the possibility.
(Other spells that can bring back dead party members include Revivify, Raise Dead, Reincarnate, and True Resurrection. Each spell has different requirements, costs, and effects.)
That said, there are certain quests (Tomb of Annihilation, for example), where the whole point is that PCs cannot be resurrected, and it is up to the party to cure the land of the curse that prevents this.
In the meantime, since Resurrection is often not a straight-forward event, it might be worthwhile to roll up a new character, or perhaps take over the role of an NPC that has joined the party, or whatever, as a stand in so you're still a part of the game.
Otherwise, if all of these are not a possibility in your game, you will have to roll up a new character. As for what the character level is, that is something to discuss with your DM. Boosting your PC level would depend on the level the rest of the party is at.