There's a big difference between "my video card is out of commission" and "my PC fried my video card".
So we need to be clear about which it is, and if the IT guy did actually say your PC fried your video card, what did they mean by it?
Bitcoin mining viruses are a real thing and not unheard of.
There's probably not a whole lot of point giving troubleshooting advice on a system that may well be infested with malware and pirated software. And you can't troubleshoot your graphics card (e.g. check temps) because you don't have it currently.
Formatting the drives on your PC isn't "too drastic" though. 1) it's actually a fairly easy thing to do, as it setting Windows back up. 2) if it is a malware issue, you might need to to get rid of it (although some very nasty Malware will survive even that) 3) if it is bitcoin mining malware that's causing issues and is killing your graphics cards, pirating stuff seems like a false economy on top of every other reason it's a bad idea.
I think you should format the hard drives (erasing all partitions) and then perform a clean installation of Windows. Make your Windows install media on a different system (one without malware / loads of compromised software on it).
After that, run deep scans with things like free Malwarebytes as well as Windows Defender.
Then you might be in a position to investigate the GPU when it's back in your hands.