George you can indeed get your CDL after a DUI as long as your license are restored. Most companies are not going to mess with you until it is at least 5 years old though.
It seems in your case you are already working at and have a relationship with the company that will employ you.
This leads me to believe that you are in much better shape because you already have a job. That is assuming they know about the DUI.
If they don't, I would suggest informing him prior to you spending the money to getting the CDL.
If his insurance permits without an increase in premiums he may not care about the DUI since he already knows you and wants you to keep working for him.
However, if the insurance does not permit, he may not be willing to take on that extra expense. I don't want you to get it and be disappointed.
Good luck man, let us know how it works out for ya.