Correct, there is no simple update to change versions.
If you select the host in vCenter, look at the area above the tabs to see the version information.
Wow, that is embarassing on the version info! I knew I had seen it before, but of course it was hidden in plain sight!
Thanks for confirming that I can't upgrade. That makes it easier in some ways and harder than others, I guess.
If you have any local storage that hosts VMs I wouldn't want to do a direct install unless you had previously created a separate LUN for ESX.
Not sure exactly what you mean. Obviously I would storage vmotion the VMs to a non-local volume before the upgrade if that is what you were getting at.