Hi,
The Retriever I have at the moment had a similar background. Solid and consistant obedience training is the key. Use food rewards and incentives and plenty of gentle praise. Obedience will increase his confidence and trust in you and will make him a happier dog. My Retriever took three weeks to heel at all times and he had never been on a lead before. It took about the same to establish his recall, sit, and down. Stay took a little longer! Good luck - it's worth it!