I've already installed and labored template that has been through many changes according to client need. However am in large problem like integrating it with existing data. He curently have a lot more than 1400 posts with 400+ tags,80+ groups ,12 pages(also now i've added many pages). Now i must import all of the existing data into new wordpress(3.1). Can there be any tool or extension to get this done. Or please advice how must i handle this? I attempted using wordpress importer which did area of the posts however wearing down as it is too big. Help me.

In case your import stops midway with an article, odds are that PHP arrived at its max_execution_time. You are able to change this value inside your php.ini file, or break your import file in two, and resume in the article which was last imported effectively.