Realistically, this is something you should test.
LANDesk itself is (in this case) just a tool to get the software where you need it, the install itself will then vary wildly depending on the command-options you've used (or if you used batch-based installation, what command-line options you've given MSIEXEC).
There's no "simple" answer to be given here, since a lot of it depends on how you install the package.
In this particular scenario, I'd suggest simply cutting down the target-list. You've got inventory from the clients, so simply set up a query to target all PC's which do NOT have Outlook 2003 (or have a version that's older than 2003).
Otherwise, if you cannot do this for one reason or another and have to get Outlook to every PC, I would advise simply setting up a test-PC (maybe from an image of a 'real world' client in your environment) and run the job against that PC.
Testing of any package is strongly recommended by LANDesk and certainly part of any ITIL process.
Hope this helps somewhat.
LANDesk EMEA Technical Lead