I'd be insisting on another conversation with the specialist before making any decisions. You need the correct info to make the right decision for yourself. DCIS appears to be a bit of a black area for them as to take the 'wait and see' attitude or not as they cannot determine which will turn bad in time.
If you are a worrier and your breasts are not the most important things for you then go for the mastectomy - get it all over with.
Was reconstruction mentioned ? If possible have this at the same time to minimize the times you will be in hospital.
Is time on your side ?
Ask ask ask and don't make any decisions until you are comfortable with what is happening.
You are in my thoughts.