Training on the 400F for me took 4 months from start to finish. The classic will take alot longer due to the fact that line training can only be done on the freighter which doesn't have alot of the shorter sectors like the pax fleet. Note: your line training if you are joining the 400F fleet will be done 95% on the pax 400's.
As far as which CAD exams you'll have to sit.....depends on your previous a/c type experience I think. Not sure about now, but in the past guys joining with only mil fighter time had to do alot more exams, even to the point of going to Adelaide with the SO new hires to do some ground school and exams there. I guess the CAD didn't appreciate F18 time as multi engine......