The question isn't clear, meaning there are many "variables" to your question, and thus a variety of solutions which you can implement to solve the specific permutation you're looking for. But I'll try to answer your question with some considerations and suggestions:
- "[A] new CSV is uploaded onto the Drive (replacing the old CSV in the process)." Are you sure this is happening? Every time you upload, say a hello.csv to Drive, it adds a new hello.csv file one rather than replacing an existing one with the same name. You would have to have an application that knows or can look up the original CSV Drive file ID and explicitly replace the file contents or upload a new version of that file.
- If you do replace the original file via one of those two techniques, track the changes to that file via the Drive API, meaning your app can take action as soon as that file has been updated. See this page in the docs to learn how to detect changes.
- The comment in the OP makes a suggestion from another SO Q&A, however that solution does not address the OP's question. Instead, it imports a CSV file to Google Drive as a Google Sheets (file) -- the CSV file never makes it to Drive as per the OP. Also, the OP is requesting something more than a mere import.
- However, with that said, the OP's final request was: "[My] Google Sheet will pull the new data and replace it over the old data." There are 2 ways to do this:
a) The simplest/easiest way is to just overwrite all existing data in the Sheet with what's in the CSV file... old data, new data, it doesn't matter. Once the new CSV file has been imported and new Sheets file created, you can delete both the old CSV and corresponding Sheet. The (new) files can have the same names as their predecessors no problem. For that, build a solution similar to the SO Q&A mentioned above -- the CSV file will already be in Drive, so just create a new Sheets file and use the content from the CSV file on Drive (rather than from the local filesystem).
b) If you only want the deltas, you need to keep a copy of the old CSV and "diff" it with the new CSV, and only overwrite the rows that have changed, a much more complex solution, and one in which you'll have to use the Google Sheets API (because it's for spreadsheet operations while the Drive API is used for file operations).