So you want to use Google Apps, below are links to help get you started. It is important to know that once you edit your domains MX Entries, your current hosting provider is no longer hosting the email services for your domain. As such any support for users of Google Apps is provided by Google, NOT your domain hosting provider.

Below are links to Google’s Support site for setting up Google Apps.

Google Apps Setup Guide: http://www.google.com/support/a/bin/answer.py?hl=en&answer=1186224&rd=1

Google Apps MX Settings: http://www.google.com/support/a/bin/answer.py?answer=174125

NOTE: Google may require domain verification by creating a TXT record.