Download the Google Apps Sync tool from here: https://tools.google.com/dlpage/gappssync.
For Google Apps MX records click here.
Note to setup GASMO you need up to date service packs for XP - SP3 and Vista and for Microsoft Outlook 2003 - SP3, 2007 - SP2. The download link is provided in the GASMO download page: https://tools.google.com/dlpage/gappssync.