Hello Phyllis,
Thank you so much for the reply and the verification that my versions are ok!
Before I saw your reply, I saw another thread about 7.6.1 and then mention of AirPort Utility v5.6 and v6.0, and I got confused again since I have v5.5.3 and the manual update said I was current. I put a comment there but wish I had come here first to check if there was a reply.
So far everything seems to be working. I hope it stays that way. My network is simple, just the AirPort Extreme and a printer. I don't have multiple Express stations, so I hope that means I'm ok.
I've been through the same situation before, as you have, regarding the hours on the phone with Tech Support etc. And it isn't a pleasant experience, for sure.
Thanks again for the help and reply! If I encounter any glitches I will report back. Please let me know if you encounter any new issues too.
David