Change Template of Word using C#

I have a scenario where a template is attached with word document.
All the templates is available on other server say '\\ABC'.

As server name has been changed from '\\ABC' to 'XYZ', path of the template
gets lost and now the word document takes lot of time to open.

I am planning to replace all the document with template normal.dot , as
normal .dot is a global template and is available on every system.

Could any body help me a c# code on how to attach normal.dot template to all
documents. I have to fix 100,000 documents.