I need to append approximately 100 records per day so I need a good method to update the information in this field after the records are appended to the master file.
If you want to replace double quotes with single quotes, then this formula would work, too:
replace( PartDescription, '""' , '"')
Since quotes are text markers in Panorama X, you have to surround them with a different set of quotes when you are searching for the quotes themselves.