Greg completed junior doctor positions across New Zealand for General Surgery training and obtained his FRACS in 2020. He pursued a Master's degree focused on diverticulitis management and gut microbiome studies, which earned distinction status.

Subspecialty colorectal training followed through the ANZTBCRS programme, including Fellowships at The Royal Melbourne Hospital, The Women's, and The Alfred, with CSSANZ membership. Additional Fellowship training in complex cancer surgery and robotic techniques occurred at Peter MacCallum Cancer Centre, where he gained Da Vinci platform credentials. He received the ACPGBI travelling Fellowship to study pelvic cancer surgery techniques at leading UK institutions.

He returned to Christchurch in 2024 as a Consultant Colorectal and General Surgeon at Christchurch Hospital, serving on the Pelvic Exenteration team while maintaining teaching and research involvement as Clinical Senior Lecturer at the University of Otago.