Updating ERA is just downloading the latest version from DriveThruRPG and installing over your existing version. The same for all book packages, you obtain the new versions, start ERA, use the book installation feature, and choose the new files.
As long as you didn't make any changes to the files includes in ERA, that is all that is required. This scenario will keep all off your saved characters and adventures intact.
If you edited the sample configuration files, or customized the skills, categories, etc, you should install to a different directory and then overwrite it with your changes + bring back your characters and adventures. Or the other way around, move your current version somewhere else, install to the original location, and then bring back your personal content.
Some of the updates will require less files instead of more, which is the case in this version, since a lot of image files are no longer needed. For those situations it is also recommended to do the fresh install and only recover your characters, custom files, etc.
In any case, it is always a good idea to do a backup before updating, to check that everything is working as you need it before committing to the new version.
As regards notifications, I always try to post here with a summary of the more relevant changes as soon as the update is available in DriveThruRPG, but you should also get an e-mail from them once the files are uploaded.