Thank you @linux4me2 and @joyously. I am reassured by your comments and suggestions. I will let you know how the update goes.
linux4me2: you are correct. My site is on WP 4.9.8. All plugins are supported and have been identified to run on WP 5.0. The only issue is the now unsupported theme picolight. I am more than willing to change themes but am not clear the best way to do so without taking down my site in the process. For example:
(1) can I upload Twenty-nineteen or another supported theme and modify it on WP 4.9.8 then upgrade to WP 5.0, or
(2) can I upgrade to WP 5.0, continue to use the classic editor (which I assume means tinyMCE) and reasonably expect my current theme to continue to function correctly?
Number 2 would be the preferred choice for obvious reasons as it would allow me time to graduate to a more current theme and Gutenberg.
