Is accepting work completed after swearing to refrain from continuing to deal with the person considered a breach of an oath, and is it considered an oath of divorce?

The ruling on breaking an oath differs according to the intention behind the oath. If you intended by the oath an oath by Allah Almighty, then you must offer expiation for an oath (feeding or clothing ten poor persons, or fasting for three days).

If you intended divorce by the oath, then it is a divorce that takes effect upon breaking the oath, and this is the view of the majority of scholars. Shaykh al-Islam Ibn Taymiyyah holds the view that an oath of divorce not intended to effect a divorce, but rather for threatening or emphasizing, is treated like an oath by Allah, and requires expiation for an oath, and does not result in divorce.

According to the prevalent fatwa, if you broke your oath and intended divorce, then the divorce takes effect, and you may take your wife back as long as it is the first divorce and she is still within her waiting period ('iddah).