Well if you want the person to manually have to reset the hero, you can find in the object editor, how much it costs to revive it (change to 0). Then you can go to gameplay constants and modify how much additional gold you pay per level that the hero has (change to 0 also).
If you want it to automatically revive, you have to use triggers. It is simple to revive a hero using triggers, so don't be afraid to use them.
-Demonfaze