Migrating Exchange 5.5 to 2003

Hello
I work at a company that has just been sold.

Right now we are using Exchange 5.5 but the plan is to upgrade to 2003.

The server is in an exchange organization with other servers at other sites.

I was thinking of installing 2003 on a new server and creating a new organization and moving the mailboxes from the 5.5 to the 2003 in the new organization.

And after the mailboxes have been moved, just remove the server from the organization without saving any information.

Is this the right way to do it?
If yes, what tools will I need to do this, and do you have any advice?
If not, what would be the best way?