Hey Cooper,
HTML of the Eloqua form is not dependent on the processing step you set for the form. Once you have decided the form fields, you can go ahead and set up the processing step in Eloqua as you want it to be. Even if you change the form fields later it won't affect the processing step. You will just need to paste the new HTML div tag of the form and replace it with the earlier one on your landing page.
All in all you don't need to disable and enable the processing steps again. You can keep it enabled and once your lading page is live, make sure everything is set up correctly in Eloqua.
Hope it helped.
Ankit