<p>I just want to create a C# program which will read a word template and create n number of copies of it with mail merge feature.The data to replace is Name and Address the rest of the things in the template should remains the same. Can any one tell me how to do this ?</p>

You can use Aspose.Word for handling the Word Object model without having to have office installed (to use interop) where the program is supposed to run, i'm using Aspose.Word to generate word  documents.
Link to Aspose:
http://www.aspose.com/categories/file-format-components/aspose.words-for-.net-and-java/default.aspx
And it works quite decent :)