1. You indicate in the instructions that the best approach is "to backup the current files, then upload the new files to the same location." Would you recommend renaming the current folder which contains v. 2.2 to phpScheduleIt.old, and then create a new folder phpScheduleIt to which v. 2.3 would be uploaded? What happens to the scheduler when the current folder is renamed? Does it just disappear until I create the new folder and upload the new version to it?
The backup/new folder approach is just a recommendation for safety and zero downtime. You can overwrite your existing files if you haven't made any customizations or changes. This does make downtime possible though, since the 2.3 application will not work correctly with a 2.2 database schema. You can work around this by manually upgrading the database, though.
2. How does the automatic database upgrade work, exactly? Do I have to re-enter the existing database parameters? Is there any risk to the data?
There are two ways to upgrade. If you're running on your own hardware and have a database user with sufficient permissions, you can run the automatic upgrade
You can also run the manual upgrade. This would be necessary when you don't have a user who can alter tables, which is typical of hosted solutions. You can also run the manual upgrade if you want to upgrade the database prior to upgrading the application. This would facilitate zero downtime deployments.
Both upgrade approaches just applies the changes necessary to made the database work with the current version.
Hopefully that helps! Please let me know if you have any other questions.