This qualitative case study aims to investigate the impact of a specially designed professional development course on three aspects: English language instructors' (1) knowledge, (2) skills, and (3) self-efficacy in integrating AI into their teaching. Cognitive apprenticeship and socio-constructivism set the theoretical foundations of this course. Working with 20 instructors at university, the researcher used two data sources (participants' opinions and their recorded lessons) and four data collection tools (pre-post course interviews, weekly-assigned implementations, their self-reflections on their AI use, and feedback on the course) to evaluate the impact of this course. The data suggest that this AI course for English language instructors likely made a significant difference, enhancing AI integration into teaching. This training could serve as a model for AI-ready instructors, improving their knowledge, skills, and self-efficacy. There are also some data that highlight challenges and limitations, unveiling different aspects of this complex field of study.