I already have an earlier version downloaded but not currently installed. Can't I just update the old version in game or do I have to download this new installer that I was notified about when logging in today?

Yes you will have to redownload the entire game installation I am afraid.

If your earlier version is earlier than the EE, you might as well download it again. The EE update is almost as large as the entire game, and it is troublesome to download.

If you already have the EE, you should let the Launcher download patches, because these are much smaller.

I haven't played it in so long that I don'y even know what version I have installed. Think it is EE though. Thx for the tip.