static void Main(string[] args)
{
XNamespace ns = XNamespace.Get(@"http://schemas.openxmlformats.org/wordprocessingml/2006/main");
byte[] byteArray = File.ReadAllBytes(@"C:/Users/Alexander/Downloads/WordTest.docx");
using (var stream = new MemoryStream())
{
    XDocument xdoc;
    stream.Write(byteArray, 0, byteArray.Length);

    using (WordprocessingDocument doc = WordprocessingDocument.Open(stream, true))
    {

#region Openxml.WordProcessing

var paragraphs = doc.MainDocumentPart.Document.Body.ToList();
Table tbl = new Table(File.ReadAllText(@"C:/users/alexander/downloads/tablecontent.xml"));
var bookmark = paragraphs.SelectMany(p => p.Descendants<BookmarkStart>()
                                           .Where(bm => bm.Id == "0")).FirstOrDefault();
doc.MainDocumentPart.Document.Body.ReplaceChild(tbl, bookmark.Parent);

#endregion Openxml.WordProcessing

#region LINQ TO XML

XElement xtbl = XElement.Load(new FileStream(@"C:/users/alexander/downloads/tablecontent.xml", FileMode.Open));

using (StreamReader sr = new StreamReader(doc.MainDocumentPart.GetStream()))
using (XmlReader xr = XmlReader.Create(sr))
    xdoc = XDocument.Load(xr);

var test = xdoc.Elements().First().Elements().First().Elements().SelectMany(e => e.Elements()).ToList();

var startBookmark = test.Where(p => p.Name == XName.Get("bookmarkStart", ns.NamespaceName) && p.Attribute(XName.Get("id", ns.NamespaceName)).Value == "0").First();

startBookmark.Parent.ReplaceWith(xtbl);

using (XmlWriter xw = XmlWriter.Create(doc.MainDocumentPart.GetStream()))
            xdoc.Save(xw);

#endregion LINQ TO XML

using (FileStream fs = new FileStream(@"C:/users/alexander/downloads/WordTestModified.docx", FileMode.Create))
{
    stream.WriteTo(fs);
}