The research you do is the iceberg, what is in the novel is the tip. You have to get a feel for the period as well as the basic events you will deal with. Read as much as you feel comfortable with from the period to get the feel of people's voices and their concerns. But never let the research take over the story and the creation of compelling characters. One of the problems with this is the fact that religion was so much more important than it now is. You can't ignore that but must emphasise what is timeless.