How much should the dialogue(/narration) in historical fiction be 'Austen-esque'?

I'm debating giving my novel a historical setting (probably either 1700s or 1900s, since there are events in both that tie in very nicely with the plot). The problem is I'm intimidated by the dialogue(/narration) aspect. I have no idea how to write historical speech. Dialogue is a weak point of mine anyway, add in making it feel believable and not forced in a historical context and I'm completely…