I sold a truck and 5th Wheel RV and provided owner financing. Need to repossess

The RV purchaser registered the Truck and RV in Oklahoma where they give the title to the new owner instead of the lien holder. I have tried to get repossession titles from OK and they refuse to give them to me because they needed special wording in the promissory note that I was unaware of. Of course I did not know the person I sold the RV to was going to register the RV in OK. He does not even live in OK. He is late every month with payment, he has allowed the insurance coverage to lapse on the vehicles. I only found out when the Insc company notified me the coverage has lapsed. He keeps moving constantly into different states to avoid repossession. The promissory note stated that I must be informed of the RV and Trucks location, both RV and Truck must be covered by Insurance, I must have current phone numbers at all times, the payment is due on the 1st of each month (no grace period). Every one of these requirements have been violated in the last year. I need an attorney.