Don't let the above post scare you unless you're not proficient in the basics. That being said, have the flows and callouts down cold before setting foot in the sim. That's what will get you the door treatment.
Also, attitude is VERY important. Show them you're willing to do what you have to do and then some, and you'll be fine.
With the limitations, don't worry too much about the autopilot, and FMS stuff. There are only a couple of them that mean anything to a trainee, and they'll go over that in class. If you still don't know what the important ones are, flag down someone on an overnight in the hotel. Spend your limitations time learning the speeds, weights, and engine crap.
Spend a little time with the systems stuff before training, but don't give yourself a headache with it either.