One night the lights went out and I went down stairs to reset the breaker. Made sure it was all the way off, then flipped it to on. A loud buzzing electrical noise scared the life out of me and a spark shot out of the GFCI. It left all the rooms upstairs with no power (except the bathroom), and one plug in the living room. Two days later there was an intense storm that left the whole neighborhood without power for 9 days. We changed the GFCI during and when the power came back, the rooms were still dead. We've had a family friend come and look at our breaker box and some of our outlets and we can't seem to find out what is wrong, as of yesterday we lost power to even more of the house. I have tried replacing breakers, we replaced all the GFCIs. And then tonight one of the breakers tripped on one of the "dead" circuits. Should I be calling an electrician? Should we have all the power off? We're very lost on what to do right now.
Check for a "Lost Neutral" and "Lost Hot".
If this is broken for your whole house, that is 95% likely to be a problem that the power company fixes for free. Of course if cost is no object feel free to let the electrician tell you that, but for budget-minded it's worth looking for.
Testing for a "Lost Hot"
Your panel will have well possibly zero, but most likely one or more "2-pole breakers". These are breakers that are double-wide, or, that have 2 handles with a visible "handle tie" between them so they throw together.
Shut off all your 2-pole breakers. Now go around and check all common outlets and lights. Are around half of them stone dead but the rest work normally (the same ones that worked normally before)? If yes, that is test #1 and continue.
Now turn all those 240V breakers back on again, and note which appliances they are for, and turn all those appliances on that you can. Now go check the formerly dead outlets. Are they live again (but maybe a little weird)? Yes? Conclusive proof of a lost "hot wire".
That is super simple and the power company should have no trouble recognizing it.
Testing for a "Lost Neutral"
This is easier done with a voltmeter. A simple novice-friendly voltmeter is the "Kill-A-Watt" appliance energy monitor, sold all over.
Despite what you've heard, normal North American power is actually "120V". (with most houses seeing more like 121-124V).
Check outlets all over the house. If you see two groupings of voltage, some significantly under 120V.... and the other group over 120V by about the same amount... that indicates a "Lost Neutral". Shut power off immediately and report the problem to the power company as an outage.
This happens because the electric service drop from the power pole to your house, go look, it 1 bare carrier wire with 2 black wires wrapped around it. The carrier wire is attached at both ends and carries the weight of all 3 wires. It whips in the wind for 30 years and metal fatigue breaks it. This carrier wire is also the neutral wire, and it's the most likely to break.
Don't get into too many details with the customer service agent, because their job is to avoid "rolling a truck", and your job is to make them roll a truck. Only a line truck can fix this.
The power company may argue with you, saying "We can't see a problem on our end" -- Yeah, that's because they can't see neutral because their smart meter does not connect to the neutral wire in any way.
But the line worker will understand "Lost Neutral". Note that for Lost Neutral to be apparent, you need a big 120V load on one of the two phases. But you want one that won't get destroyed by the weird voltages.. If it's the only large 120V load, you can run a space heater or a hair dryer - anything more sophisticated than that could get fried by the high or low voltage. Make sure all your costly 120V electronic loads are unplugged, particularly fridge, microwave, laser printers, TV etc., and certain computers which care about voltage.
"I can't go for hours without my fridge" -> you won't have to. If there hasn't been a recent hurricane or ice storm, they usually come out in an hour or two for a reported outage.
The answer from @Harper deals with the most probable faults.
There is one more possibility - a major rainwater or other water leak somewhere in the house. Depending on a lot of factors, some leaks are not immediately aparent or may happen in the attic (if there is one), in the basement (if there is one), in the crawl space (if there is one) or in some less often visited spaces.
Just go and inspect these places.