Hi jasonw30638826,
The Add a field functionality is pretty mature and should not cause any issues, but then we don't know what you are trying to add and how many rows there are in the table.
Adding a field will cause the DB structure to be updated, thus taking locks while doing so.
If the table has millions of rows, it can cause issues. We
will suggest that you take the system offline for external users, probably stop WFSERVER and MTA and then make the update.
Regarding editing the existing field name, you need to go to schema and find the corresponding attribute, only to change the label or name as per your requirement.
Then you should update the DB structure as well.
Regards,
vipul