The level of the quest you are offered is random (30, 32 or 34).
You may delete the quest and re-acquire it if you like without any penalty. This is recommended if you are askew to kill one of the scarce mobs, such as a lesser mimic.
Completing the required kills immediately completes the quest, and Master Eldin Necrosis immediately offers it again.
Only the level 34 version rewards armor. Also, the level 34 quest reward is listed as "You will receive a piece of Ravenring armor", but you also receive an unlisted coin reward. Therefore the actual minimum amount of coin is an estimate; no amounts less than the value shown have been recorded.
Most of the monsters required for this quest do not respawn.