If you meet all the other qualifications including driving for over 6 months in the last three years. You will be considered an "experienced" driver. Once you complete the mini orientation course you can opt to go out with a trainer for a week to get a feel for things.
If you have no experance but hold a valid CDL you will go through the entire training program and then out with the trainer for 21 or more days.
Dont worry too much about your driving ability, some recent grads show that can barley keep it 'tween the ditches and Maverick trains them up to be good drivers.