n8n Email-to-Sheet Automation

I have a Gmail inbox that already holds a backlog of messages and will keep receiving new ones. From each email I only need six specific values that sit inside the body text—no sender info or attachments. I want an n8n workflow that:

• Pulls all existing Gmail messages once, extracts those six fields, and writes them to a dedicated Google Sheet.
• Keeps listening afterward so every new email is parsed and appended automatically in real time.

Please build, document, and hand over the workflow file (and any helper credentials/variables clearly marked) so I can import it into my own n8n instance. The solution must run hands-free once installed, and the sheet should never duplicate rows. Feel free to propose the parsing logic—regex, HTML selectors, or another approach—as long as it is reliable for the typical Gmail message format I will provide.