Hi Baffour,
If your data is already a feature class, then you may want to look into publishing/overwriting workflows with ArcPy. Let me know if this is the case and I can point you to other resources.
If you are looking to specifically publish from a csv (convert the excel spreadsheet to a csv), here is a sample of how to perform the initial upload and publishing of a csv file to a hosted feature service: developer-support/upload-publish-CSV-multipart-arcgisonline.py at master · Esri/developer-support · ...
You will need to modify this script in order to bake in an overwrite procedure. CSVs which are uploaded to ArcGIS Online and used to create a hosted feature service have the ability to overwrite the data into the existing feature service which will be reflected in the web map. Read this documentation for more about the overwrite functionality.
To script this, use the following rest api documentation, specifically the overwrite parameter and the update item and publish item call to add this functionality. You will need to update the already publiished hosted feaure service and then submit a publish call for the same item: Update Item, Publish Item.
I would also recommend using the status call to check for progress.
-Kelly