Sadly, no, we wouldn't be able to integrate that much without cooperation with LiveJournal! We use it to make sure people don't lose control over things that they (or somebody else) imported, but we can't do single-sign-on, alas.

If the page shows success, you are good! it may take a bit of time for all the comments and entries your OpenID 'account' posted to be shifted over to your DW account (looking up all of them is really hard on the database, so we do it veeeeeeeerrrrrrry slowly in the background) but there's nothing more you need to do yourself; the site will do the rest of it for you.