Who can help me with OVERLORD?

[GLH]

Perhaps someone can help me with this game.
I've some questions:

Normally all the quests in the list have a little Overlord-Sign, but the one, where you have to kill the giant snail and take back the goldwagon, has a little minion-sign. I already killed the giant snail and found a big treasure, but not a gold-wagon. The quest is not counted as quest (in the tower, when i activate the tower-heart), but when i go to the Arkanum Mine-Area, this quest is always listed.
Whats the solution for this?

In the desert, there is a giant sandworm. I already tried all four minion-classes, but can't kill that sandworm.
How can i beat him?

Also in the desert. There are some bone-barriers.
How can i destroy them?