How to extend the existing Web Service and called in window service ?

Hello All,

  If i add more methods in existing web service. Will it harm to the basics of web service?

I like to add insert product,product variant etc(product details) methods in web service.

Will make use of web service URL in my window service which run on 5 min interval.

For window service will provide path of XML file.Will read the file and called method from web service to insert product details in appropriate table.