What type of training is needed to assist in a morgue if I am a certified medical assistant?

Depends on what work you want to do. A morgue employs many people with little or no training to move bodies around, clean up, maintain instruments, do clerical work, etc.

Autopsies are performed by a forensic pathologist. But they might have positions for someone with medical training to assist. I would ask what positions are available then see what trianing is required.