SharePoint 2010 Custom Workflow Upgradation

Hi ,

I have a workflow(Sequential, Created in VS 2010) already deployed in a SharePoint 2010 Production Server. I have done some modification on it in our Dev Server and want to re-deploy it in production, so that existing workflow instances are not affected.

Can you please provide me a guide, how I can  proceed.

Please reply me at ariteo_job07@yahoo.co.in if you want.

Thanks And Regards

Aritro