Salesforce to Google Sheets Integration

I have an app in Google Sheets (gs) which I need to connect to a Salesforce application via oauth2. This app will need to be available in the Workspace Marketplace, and also globally available in Salesforce. Currently the application connects to Salesforce using an app within the development company, using secret + key, this needs replacing with the correct oauth flow, so that any Salesforce company can make use of the application.

You will need Salesforce experience in order to undertake this project. Communication with me is also key!