Tom, this is why you guys put in all that effort on Applescript support :-)
Unknown1, I've attached a pair of scripts which you can install in your OmniPlan toolbar to search by either unique id or WBS id. After the script runs, the matched item will be selected, and you can use the inspector or keyboard shortcuts to apply your updated status.
You can learn more about installing Applescripts in Omni applications in
this thread, just read OmniPlan wherever it says OmniFocus.