Upgrading an Arch install months or even years out of date is not that big of a deal. That’s one of the benefits of a rolling release platform.
Once after a move, an old desktop sat in a box for at least two years and I had it updated in a hour or so. Yes, you have to review the archlinux.org news feed for breaking changes, but if you follow any steps that pertain to your packages it’ll work fine.
Package metadata isn’t stored in text files because there’s an amazing technology called the database.
All you have to do is learn how to use your package manager. Spend time reading the man pages and learn the options, and you can query everything you need.