San Diego State University recently embarked on a major initiative to revitalize the Precalculus, Calculus 1, and Calculus 2 sequences. In addition to program features such as course coordination, a new active learning component led by graduate teaching assistants (GTAs) was added to each of the Precalculus, Calculus 1, and Calculus 2 courses, and a professional development (PD) program was instituted to support GTAs. There were many challenges related to workload, contracts, communication, and GTA buy-in. Here we present the evolution of the GTA-PD program through the discussion of successes, challenges, and responses to those challenges. We conclude with some of the overall lessons learned thus far, and how we are continuing to evolve.