In terms of safety - you should be pretty safe. When my dad worked on an ambulance in Rochester NY, the crime scene guys would oversee the company that did clean up - they don't want you fucking with the place at the end. They also won't let you get fucked with.
that said - that was Rochester, not sure how they do it where you are.
as for physical health, you will sweat a lot - they wear full bodysuits and gloves and masks and shit - if not, you sure as hell should be. you work with some caustic shit, not to mention the blood pathogens (mainly would not want hepatitis since it is hearty once outside the body, unlike AIDS and a few others).
as for mental health - that could be tough. seeing brains all over a wall of a bathroom is likely not something that you get used to quickly.
that said, think of it in terms of the broad picture - if you think of it as the person, it hurts. if you think of it as a body that was cells that were doing their thing and on down - the way doctors view it - then it gets far less gruesome. seeing it like a system, as you would an engine or something.