Hi there! No dumb questions, thanks for posting this.

1. To your first question. Yes, you can test the Actions (somewhat) locally and the Deno script locally. The Deno script is a bit easier to test locally, you can try to:

• Install Deno locally on your computer (https://deno.land/manual/getting_started/installation)
• Create a file with your local script fixweather.js and replace Deno.args[0]; with just the name of a local file
• Run something like deno run -q --allow-read --allow-write --allow-run --allow-net --allow-env --unstable fixweather.js

With GitHub Actions, you can use the command line to trigger workflow runs but you can't fully simulate it locally. There are two approaches:

• Use the GitHub Actions cli: https://github.blog/2021-04-15-work-with-github-actions-in-your-terminal-with-github-cli/
• Use act: https://github.com/nektos/act

2. To your second question. You can solve the error by upgrading the Flat library to https://deno.land/x/flat@0.0.11/mod.ts in your fixweather.js file.
   More info at Relative import path "ssf" not prefixed with / or ./ or ../ #45 and Error when running githubocto/flat@v2: Relative import path "ssf" not prefixed with / or ./ or ../ from "https://cdn.deno.land/sheetjs/versions/v0.16.8/raw/types/index.d.ts" #47.