Hex Edit
When you start a mission (at least with the Atreides), if you save it as soon as you start, your spice credits will be stored in byte 24354 (hex). If you've already made something in the game, the proper position will not be exactly that, but it won't change much. So far, I only noticed a change up to byte 24344 (hex). I took the offset values with xe, an hex editor for dos, which I use to edit all my savegames. And as I said, I only tested with the Atreides.
Ordos Ambush Mission 9
This Level is much more easiër then Atreides or Harkonnen. once you start with the mission, protect the mercaneries (The Yellow Allies) by building a lot of Rocket turrets, and build a wall around their Starport, if you wait until your friend has a great force, sell the walls you build and watch how the mercaneries attack the enemy.
Note: you can also save before you let your friend go, if the force doesn't scratch your Enemy Base, Load your save game to make your group stronger, and let go again.