Replace field contents can set a field to a value for all the records in your found set. You still have to do it one field at a time, but just once for your entire batch of records.
Pull up a found set of records to update.
Click the 0 radio button.
Select Replace Field Contents and use the "current value" option to set this field to 0 for all the records in your found set.
Since Replace Field Contents can change the value of a field for hundreds of records and cannot be undone, it's a good idea to make a back up copy of your file before learning how to use this menu option.
First of all, thank you so much for the quick response. Second of all, I need a bit more help.
How do I "pull up a found set of records to update"?
I figured that question out actually.
The dialogue box says that this will "permanently" change the field value to "0", as is seen in the attached image.
If I do this change, will it be impossible for me to switch the value to "1" at some point in the future?
Yes, it will be possible using the same method. I do wonder, however, why you would want to do this. You may want to consider the utility of this field.