Are you complete generating the Word doc in code?
If so, the paragraph style is set pretty easily:
Paragraph paragraph1 = new Paragraph()
{
RsidParagraphAddition = "00CB5EB1", RsidParagraphProperties = "00020731", RsidRunAdditionDefault = "00020731"
};
ParagraphProperties paragraphProperties1 = new ParagraphProperties();
ParagraphStyleId paragraphStyleId1 = new ParagraphStyleId() { Val = "Title" };
paragraphProperties1.Append(paragraphStyleId1);
The lines above the StyleID lines are just the paragraph identifier, not specific to the style, and will change for each paragraph. I just left them in there for context.
The paragraphStyleId is the "important" part. :)