Trample only applies when you're attacking, and if I'm reading this right you're blocking the 6/6 with your 5 Spawnwrithe tokens. The 6/6 will not die and your opponent will be able to kill off three of the tokens.
Now let's flip this and say you're attacking with a 6/6 trample and it's blocked by a 2/2 with indestructible. Trample doesn't care if a creature dies or not, just if lethal damage was assigned to it. If something stops the creature from dying, e.g. indestructible, protection, or regenerate, the extra damage will still trample over.