I finally gave into the constant messages to update -- said it would take several minutes. After more than an hour, with the phone getting pretty hot, the phone battery ran down so I'm not sure if that affected the installation of the update.
Anyway, after fully charging, I'm finding several problems.
Wi-Fi: The wi-fi connection previously worked well OK, but I'd have to turn it off to use 4G or 4G internet connections in non-wi-fi areas. Now the phone no longer indicates it's connected to wi-fi, but rather alternates between starting and connected -- and also alternates between two available signals. And even within one foot of the router, it indicates a "weak" signal.
Pictures: The picture taking function no longer works. The photo program loads, and you can take pictures, but they are not available anywhere I can find to send, attach to contacts, etc.
Music: The phone said I had very little capacity left in memory, so I transferred all music to a removable flash drive that I'd installed long ago. But neither of the two music apps can find the music.
I find some aspects of the ICS very pleasing aesthetically, but it's frustrating that many functions seem not to be working at all, or not as well as they had. Advice? Thanks.