This requires level 40 or maybe even 50 to even start.
Solution
From GP AP:
He'll send you on another mission, this one more complicated.
This time, you'll need to enter the strange building
Reward: quest points, 1 permanent point in wisdom, some experience and 40 or so trains in hand to hand.
If you want further experience, you can try and kill the spy, not an easy task necessarily, then return his head to the guild navigator on the upper floor of the strange building. Be sure you kill the spy yourself, as the navigator might feel more than a little angry otherwise.
Baldur's Notes
GP AP, n, n,ne. All further paths will be given starting from that point.
n, search, 3n, d, kill trooper, u, s, search grass, out
n, w, d, max w, e, search for blueprints
e, enter, n, 2w, d, max n, ramp, enter, 2w, kill mechanic,
climb ladder, e, search cables, w, d, search floor, trapdoor
install switch, flip switch, portal, steal motherboard from computer,
flip switch, portal
* n, search, 2n, search (go back to Atreid) say I have the motherboard