Exchange 5.5 to Exchange 2000

I have been tasked with upgrading our mail to Exchange 2000. At first, seemed like an easy thing. Then I looked at the migration wizard and such and realized this is going to be a major undertaking.

What I am looking for is things to be aware of and attentive to while trying to do this upgrade. We are a smaller part of a division, but we have several remote users as well as in office.

Any advice would be GREATLY appreciated.