I read all the posts. I googled.
I'm putting in the GFCI (with alarm if available).
Now, here's all the information that I've picked up, and where my level of understanding is at the moment - which is much less than the understanding of many of the members. So I'm a layman, setting up an aquarium. I'm not setting up a power plant. I'm hoping my level of knowledge at this point, is sufficient to keep both myself, family, and finny friends from being fried.
Here's what I now believe I understand, from reading all the posts and also googling up a few articles:
Ground probe without GFCI is bad (according to article) because it provides a path for current, which is what you don't want. Without a path, current goes no place. True you're preventing yourself from getting a shock when you put your hand int the tank. But Ground probe value is debatable. On the other hand, there's no debating the value of the GFCI outlet. I see now there are adapters for about $25 you can plug into existing. I just called a local electrician and will get a quote on installing a regular one. I could probably do it myself but let's see what she will charge.
People have recommended having 2 independent GFCI outlets. I can see the advantage, but I don't think I'm going that far. People have recommended plugging everything into the GFCI but many say, at least the return pump should be in a regular outlet in case of tripping. Then others have commented that faulty tripping almost is never an issue any longer. And there are alarms.
This is a complicated hobby. When experts disagree, it's not easy to make decisions, especially when you're not an expert yourself. But as a home hobbyist, I've come to the following plan here:
-have a GFCI installed or install it myself
-forget the probe (I'll check my heater though, as maybe it functions as a probe - just checked, and no it doesn't

)
-plug everything into the GFCI except the return pump, which I'll plug into a regular outlet, but watch it like a hawk and make sure it's well away from wetness. That part may prove tricky. Where do people position their return pump, usually?
-make sure there are drip loops wherever needed
Am I forgetting anything, or have anything wrong?
Feel free to comment. Thanks for all the answers. It's gotten me to here.