Is this OK; that is, is he telling me the correct ID?
Yes, the 12-digit IDs are now the current format. However, 9-digit IDs are also supported for backward compatibility. That is, you can still connect to older Host installations from newly updated Viewer.
Just realized that the "Check for Updates" button on my current version doesn't work! So manually downloaded and installed new version.
Automatic download of an update file was implemented only recently. That's why it's not available in version 6.3 and earlier.
P.S. We try to improve update-related features with each release. Now you can automatically update both Viewer and Hosts, meaning that you just need to click a button and the program will do the rest. This tutorial
explains how, see "Updating Viewer Method 1" and "Updating Hosts Method 1".
Note that the word "automatic" here doesn't mean that the program updates on its own without the user's consent. It is the user who makes a decision and initiates the update process.