If you use a Web Connection to connect to your Google Docs account you only need to enter a sheet name. If it exists FME will treat it according to what you set in the feature type settings (Feature Operation, could be Update, Upsert, Delete or fme_db_operation if you want to handle it per feature).

I think, but haven't tested this, you can also add the shareable url that you can get in Google Sheets.

Hi @thane.taylor If you want to check if an URL exist (the shared Google Sheet url) you can use a HTTPCaller and use the HTTP Method HEAD. This will just check if the file is there without downloading it - so its fast.