My van is over heating, what part do I need to replace? on 1994 Nissan Quest

When I'm driving, the gage stays at cold, goes slowly to "M",
stays there for a few minutes; than goes quickly higher. After that smoke comes out from under hood.

Asked by for the 1994 Nissan Quest
Need to first determine WHY the van is over heating. Here is a check sheet to help you: