This information should be easily queryable from the Software|Application Suites information in inventory. Which is gathered by the inventory scanner from Add Remove Programs on your clients. You will want to ensure that your inventory scans are up to date and recent and that software scans have been done recently on the clients, then just create a new query where O3K SP2 either exists or does not either way will tell you what you need to target your package.
This came up on the old forums a long while back.
My response from the old forums:
This MS KB Article will tell you how to determine the Office 2003 Service pack.
I was able to determine the service pack using inventory by going to
Computer->Software->Application Suites->Application Suite->Microsoft Office Professional 2003
and checking the version property
The version should be 11.0.7969.0 as described in the Article.