>How do I go with installing tools of 401? Googled no help.
Use the link Woody posted earlier to download the 4.0.1 tools installers.
>I already installed host in my 4.0.2 and the game I want to play (very big downloadable), so I kinda don't want to go from scratch.
Uninstalling/reinstalling/updating Player has no effect on your existing virtual machines. To your host, a VM is merely a document/file.