So, you can pull down this xbel file and call Import Bookmarks from the Bookmark Editor. You'll still need to download the appropriate icons from lj but that should be pretty easy. I used the standard user icon - for userinfo and converted the livejournal.ico from ms-windows icon format to png for the journal entries.
This will give you two smart bookmarks where you can enter a username and it will bring up either their journal or their userinfo. You can also type "lj username" or "userinfo username" as a URL and you'll get the same. It should be fairly obvious how to extend this to get pictures, memories, friends, friendsfriends, etc.