Your tickets may be electronic, and you’ll get an email with the reservation link. If you don’t see them soon you should probably talk with either a ‘deployment specialist’ or the person who hired you. If they’re paper tickets, there’s no tellin’ when they’ll arrive (some folks have had the FedEx truck pull up to their house with the tickets even as their taxi for the airport was honking outside). I know that’s not very reassuring but ’tis the way things work sometimes.
Not sure what to tell you about the laptop backpack. If it’s not much bigger than the laptop itself it should not be a problem.
Right now things are stressful because it’s all unknown. Once you hit the road it’s a lot easier to relax. You’re about to meet some very interesting people…