How to determine if my gas fireplace can burn wood safely?
I'm not a Chicken Little type, but there's no way I'd do that, for a couple reasons:

You don't know what's behind the surface masonry. Wood-burning fireplaces have multiple layers of insulating masonry to handle the massive heat that can build up, protecting the wood framing around it.
You don't know that the flue will handle creosote, sparks, etc. Wood fires are messy and produce much more flame and embers than a gas unit.
It's probably not designed to draft a smoky wood fire. You'll have billowing smoke in your room on a regular basis. It's carcinogenic.
You'll almost certainly void your homeowner's insurance (and make yourself legally and morally liable for death and dismemberment of occupants).

The answer to your actual question (&quot;How do I...&quot;) is that you have a specialist stop by. They'll be able to see things that you and I can't from here. It's just not a question for the internet.