If you really are unhappy with your "basic" character after the first scenario, then we'll review the situation again. Until then, I'd definitely prefer if you just stuck with the given classes, please
As for starting XP, you all get 400 XP to start with. You'll get more as we go along, don't worry
Also, please make sure you roll for your starting income too as you will be able to buy stuff as we go along in the scenario.
As for time zones, I'm GMT+1, but just make sure you follow the game and post whenever you feel it is necessary. One rule that I would like you to follow is that you post at least once after each one of my posts.
Oh and for home worlds and careers, please go with the ones described in the core rulebook. If you want to alter your careers a bit later on, then we can see that later on