In the old post from when the update was released a Heise article is linked, that contains indicators of compromise, and in turn links to Kevin Beaumont for the details of his analysis:

https://lemmy.zip/post/54712916
https://www.heise.de/en/news/Notepad-updater-installed-malware-11109726.html
https://doublepulsar.com/small-numbers-of-notepad-users-reporting-security-woes-371d7a3fd2d9

I don't think you'll need to uninstall. If I'm reading the article correctly, it looks like they plugged the hole in their update process by switching hosting providers to one that's even more hardened and secure. So requests from the updater should go to the correct place now and not the state-sponsored hacker.

Then in about a month, the next version of notepad++ that is released will also properly validate/verify any downloaded update files from the server.

You could also just disable the checks for updates from within the application too. Or better yet, use something like winget to handle the updates instead of the built-in updater.

I would just follow their advice, download the newest version from their site directly and use the new versions installer to update manually. I would probably do the same thing when the newest version with certificate and signature verification releases, after that I would assume you should be good to go. However its probably also worth scanning your system for malware just incase you updated during the time frame the attack was live.

Yes, that's the safe way. Uninstall, download current version, install. That's it.

Outside of being compromised already where you would have to notice and fix outside of notepad anyway. But that seems unlikely given the selective attack nature the hoster was able to confirm. If you'd want to cover that you would have to know and do a lot more.