Hello Mars - very glad you found us here and I hope we can help you get through this. As everyone has written, it's not easy. My own surgery was nothing compared to what Christine, Cheryl and now you too will be facing. They are heroes and I know you will join them in the pantheon!
I can however speak to the tongue numbness issue as I also have a half-numb tongue 3+ years out of surgery. It's a drag... but you do get used to it although it takes a bit of time. My RO had told me that sensation can return for up to 5 years post-surgery and I have noticed a bit of that. I don't believe it has had any lasting effect on my voice, especially now that I've recovered a good bit of my salivary function post-RT.
Oh and I also had an emergency tracheotomy after surgery for the better part of a week. Unpleasant, but that too passes (although I do know there are some permanent ones).
Mainly though keep in mind that we're all different. Doctors have to kind of give you the worst case scenario at some point. You may recover faster than others, you might not have as much nerve damage, etc., etc. I know getting all this news, especially in a bunch, is frightening and demoralizing. But I'm sure you're making the right decision to have the surgery. We are all here for you. As Cheryl says, it is indeed amazing how strong and resilient we become when we need to.
I'll be sending my best vibes across the pond.