Removing or Changing Installation Packages from AD OU's

I am currently test upgrading our clients from SEP 11 to SEP 12 in an OU Structure using the "Upgrade Clients with Package" wizard. I know you have to place the Installation Package(s) inside each OU and I have done so. I missed a step in one of the packages to 'display a notification message'. When I try to redeploy the package with the notification, they will not update. I was wondering if there is something I missed in redeploying OR if that is not possible; how do I remove the Installation Package from our (very detailed) OU structure. I really don't want to go through the tree.

Thank you,
James