I am sorry to disappoint you but I am not Sir Exxon!
As for the underdark the quickest way is
SPOILER AHEAD
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.Go to the Deep Gnome village to the North.
Do their quest
Take the lightstone as reward and head for the part of the map that says "Dark Cave"
After the dark cave go to the Drow City
Do excactly as the Drow tell you adding a little of common sense!
Escape.
You will be missing some good items and lots of exp however.