How to go about rewriting my old fic and posting it?

I have a fic that had 5/7 chapters posted, and then my laptop got soaked and the outline I had written got lost and I didn't have it backed up (great learning opportunity lol). Anyways, I've gone back to reread the fic and gather the few notes I had scattered around to put stuff back together and realized that there some things I'd like to change. While the storyline and interactions will mostly remain the same, I'd just be shifting the timeline of stuff. It's a cross-country post apocalyptic road trip au so the biggest thing is the weather and when events happen (along with some other details that will be edited).

I was wondering that if I was going to re-do it, what is the best practice to put this new fic out there? Is putting a new chapter out to the previous fic explaining the situation alright? And then once I finish the edited fic just post it is a regular, and maybe change the title/tags of the old one to tell people to go find it? Or should it be deleted after a while when the new fic is done and all the previous readers have made it over? Basically just want to know what would be best for the readers so I don't leave them hanging or without breaking any like, ao3 etiquette or anything lol. TIA!