There is nothing wrong with you benefiting from this experience and using it in a permissible job.
Similarly, if a person deals in haraam things, and benefits from that experience in business and handling money, then there is nothing wrong with him using this experience in permissible jobs. Islam brought the command to give up riba, deceit, cheating and other haraam things but it does not forbid any of those who have repented -- or even those who have not repented – from working in permissible fields benefiting from that experience.
As for working in the customs, the ruling on that has been explained in the answer to question number 39461.
We ask Allaah to accept your repentance, make the consequences good for you and to grant you provision by His grace.
And Allaah knows best.