One thing you should bear in mind: Your players will not do what you want them to do. They will befreind NPCs they were supposed to hate. They will bypass puzzles. Then they will engage the locals in an extended shootout. Somehow, they will do this in character.
I've sat on both sides of the table many times. I still don't know how it happens. Just be prepared with two adventures/stories/whatever. Make the second one extremely flexible, and just improvise. You and your players are on the same team, unless you'r playing Hackmaster or Paranoia.
And may the Gawds be with you.