Hi @rachelpapers,
The service ID can be found when you open the layer/table in AGO, you will see that same GUID in the service URL or in the URL of the page when you open each layer/table in a new window.
As for finding the duplicate names in XLSForm xslx file. You can do this in Excel a few different way. The new 3.14 template, or any of the new templates from recent releases, have validation on the name column to check for duplicates. However if you have been copy and pasting formatting, you will likely have removed this validation by accident, or if the template the survey was made from is very old.
One way to fix this is download the latest advanced template in Connect 3.14, and then copy all of the columns from your current survey xlsx file, into the correct columns in the new template (note that columns may have moved). Ensure to only paste values to ensure the validation does not get removed. You can then replace you current xlsx file in survey designs folder with this new one.
Another way is to copy the entire name column into a new excel sheet, and then sort it by name, just as a check, to see if you can find the duplicate values. Or use one of the inbuilt Excel formulas to find duplicates, or you can do a count, by create a pivot table on that name column, and count each unique value by using the sum function.
Regards,
Phil.