How Does Trample Work Mtg?

Trample is a keyword ability that changes the rules for assigning damage in the Combat Damage Step. An attacker with trample deals excess damage to the defending player or planeswalker even if it is blocked.

Does trample go through if creature dies?

Short Answer. Yes, that's what trample does - any damage beyond lethal can be assigned to the player or planeswalker the trampling creature is attacking.

Does trample go through prevent damage?

With trample, you have to assign what would be lethal damage to all creatures blocking it before you can start assigning damage to the defending player. You do not take effects that would reduce or prevent that damage.