Moving mailboxes from SBS2003 to new SBS2008 - NEW domain - best method

A small business I support is moving from an old SBS2003 server to a new SBS2008 server. We are not doing a migration/transition, we are "Starting over" on the new server.

Will be migrating all the programs and data, and have a good handle on all of that. However, we would like to research the best method for migrating exchange. The new box is a new domain, we intend to re-create the users and had planned on simply exporting the mailboxes from the old server and importing them to the new one. About 20 users is all we have.

1) What is the best method to achieve the mailbox migration as noted above? Remember, different domains and versions.

2) There are a couple public shared calendars and folders. Can these be migrated as above? Will it vastly complicate things?

I need to choose a method, and compile a step by step procedure we can use on cut-over weekend. We will of course do some trial migrations ahead of time. Please point out the benefits/detriments of any of the different methods proposed, since from what I have read so far there are many ways to skin this cat. Most points awarded for detail.

I have a winXP workstation to use for this process, can set it up any way needed.

Thanks for the help!