Office 2003

Is there anything I should know or do before installing Office 2003.
The current system consists of:
Server (small business server 2000)
2 Laptops (Win2000 prof, Office 2000)
1 PC (Win 2000 prof, Office 2000)
1 Pc (Win XP and Office 2000)
Where is the best place to purchase the product. We are based in Ireland
Thank you.