Mailbox moved to new AD/Exchange

We are in the process of moving all users in to a new AD and in to Exchnage 2007. I'm the only GTD user. We are starting off with new blank mailboxes by default and exporting and importing mail items where needed. I've done that with all the relevant GTD folders but as I'm now in a new mailbox the GTD plug-in is not there. Presumably I need to re-install this but any idea how I retrieve project details etc. from the old mailbox? Also, all my categories and colours are reset to default. I know that Outlook 2007 no longer stores category information in the registry but if it is stored in a mailbox, is there any way to get it from the old mailbox in to the new?

Thanks in advance for any help.

Cheers
David