Correct, Update 3 is no longer a Preview (for first batch of language distributions). You misunderstood Eduardo I think? If you HAD installed the preview version (which was build 5002 already, at least for Intel), you will NOT be prompted for the release version as it is the exact same build. There is nothing more to do. If you had NOT installed the preview, then it will show up with Check for Updates.
But, note that the release version of Update 3 is not out for all languages yet.