You may want to talk to the interventionist again and find out exactly what he is talking about - if he is going along with these types of dramatics i would question his skills a bit.
But hey i'm not a professional so maybe i'm wrong.
What i do know is that when i talk about death with my AS his response is always "well i dont want to live to be old anyway." That only serves to hurt me.
I think if i showed him caskets he'd just get PO'd, stop listening and most likely leave. Which again just hurts me.
People on drugs wont have the same reactions to things like a funeral that a healthy happy person is going to have. By the time you finish getting brochures on caskets and thinking about his death you are going to be even more upset. Instead of this do something healthy for yourself. If you want to do an intervention then do it but i would stick to boundaries. You dont have to do everything an interventionist suggests.