I am not able to edit the description text of the published windows phone app(for existing xap). - I clicked on Update App - Then upload and describe your packages - Edit the description text and save it - Then app will show Complete or Delete Submission until I resubmit the app and shows app submission status as Not Submitted.
How do I change the description text without resubmitting the app?
To update your description you must need to update your app. Just go ahead with the steps as you followed and update your app. And now a days the certification process is very fast and it will be live within hours.