hiieees Hi, welcome also.
I think I get where you are coming from and I had similar thoughts too when I got my first Pixel to install GrapheneOS.
I just had a quick look at the web-install instructions for GrapheneOS.
https://grapheneos.org/install/web#enabling-oem-unlocking
My thoughts are that just working your way through the initial preparation will test most of the device (display, touch interface, volume+power buttons). You will be testing the usb-c when you connect the device to the computer.
So I suggest, if you do wish to test, all that is remaining for you to test beforehand are the speakers, microphone, modem, wifi and bluetooth. You can test the modem without a SIM by coming out of aeroplane mode and seeing if you still get the 'emergency calls only' stuff. Probably a few ways to test bluetooth depending on what other devices/speakers you have. Wifi is easy to test with Vanadium web browsing and whilst you are connected to the web I reckon you could go to f-droid.org and find some app to test the microphone. Speakers are easily tested with listening to some of the ringtones.
That should be enough testing to put your mind at rest before installing GrapheneOS.
Also, https://grapheneos.org/install/web#replacing-grapheneos-with-the-stock-os lets you know how to revert back to the stock Google OS if that would reassure you for warranty reasons.
Do some quick tests of the hardware for a few minutes but I'd say go for it, the sooner the better.
GrapheneOS is very clever to let you choose your own balance between no google stuff and the default Android experience. In UI terms, the only big difference is that you can live with no GooglePlay at all or use the Sandboxed GooglePlay (with full control to disable it whenever you wish, or limit it to profiles of your choosing). It really is a beautiful thing.
Good luck, let us all know how you get on.