1. You accept the quest, take the machine down - are told to meet the guy in the instance.
2. You meet him in the instance, he divvy's up another quest that looks like a standard quest. -NOT-. He wants you to kill a mob with 800k+ health (and are given no special items, etc).
Apparently this has happened to some guildmates as well as others via wowhead:
There -really- needs to be a group indicator for this quest - people have to blow their hearths because the mole machine isn't usable after the turn in.