Solved it, just use the OpenXML Productivity Tool, find the name of the part you looking. Alternatively just open up the document and identify what you looking to change, like a Header or Part A or Normal.
Here's the code with sample changes:
public static void GetAndSetStyleFromDoc(string file)
{
bool styleExists = true;
using (var document = WordprocessingDocument.Open(file,true))
{
// Get the Styles part for this document
StyleDefinitionsPart part = document.MainDocumentPart.StyleDefinitionsPart;
foreach (Style style in part.RootElement.Elements<Style>())
{
// PartA can be changed for "Normal", "Header1" etc
if (style.StyleId.Value.Equals("PartA", StringComparison.InvariantCultureIgnoreCase))
{
style.StyleParagraphProperties.SpacingBetweenLines.Line = "276";
style.StyleRunProperties.FontSize.Val = "14";
style.StyleRunProperties.Color.Val = "4F81BD"; // font color
ParagraphBorders paragraphBorders1 = new ParagraphBorders();
TopBorder topBorder1 = new TopBorder(){ Val = BorderValues.Single, Color = "856363", Size = (UInt32Value)24U, Space = (UInt32Value)0U };
LeftBorder leftBorder1 = new LeftBorder(){ Val = BorderValues.Single, Color = "856363", Size = (UInt32Value)24U, Space = (UInt32Value)0U };
BottomBorder bottomBorder1 = new BottomBorder(){ Val = BorderValues.Single, Color = "856363", Size = (UInt32Value)24U, Space = (UInt32Value)0U };
RightBorder rightBorder1 = new RightBorder(){ Val = BorderValues.Single, Color = "856363", Size = (UInt32Value)24U, Space = (UInt32Value)0U };
paragraphBorders1.Append(topBorder1);
paragraphBorders1.Append(leftBorder1);
paragraphBorders1.Append(bottomBorder1);
paragraphBorders1.Append(rightBorder1);
style.StyleParagraphProperties.ParagraphBorders = paragraphBorders1;
}
}
}
}