As long as you’re very thorough about removing any linked connection from your expired e-mail, you should be OK. That includes all accounts that you registered using this e-mail, as well as all e-mail contacts that you’ve built up using that account.
It’s an exploit path to a UEFI bootkit, so at the very least you’d have to throw your motherboard away or find someone that can physically overwrite it through an external flash programmer or something. And the patch should be delivered through a UEFI firmware update, so if your motherboard is no longer supported you would have to buy a new one. And for laptops and embedded devices having everything soldered in, the motherboard is basically the whole computer, so I don’t think it’s that much of an exaggeration.
I guess it’s true that if you have ring 0 access you’re boned, bug if your ring 0 access gets upgraded into ring -2 access you are even more boned. They put those security boundaries in place for a reason after all.