HI there... there are a few people here who've had the same surgery. It does sound like they are trying to avoid the possibility of chemo and radiation. HPV related cancer usually responds well to rads and chemo, but the fallout is such that if it can be avoided it should.
The neck dissection is actually not too bad in terms of pain post op. Usually it's numbing, tightness and uncomfortable because you have drains - though it's scary looking. You will have swelling and at some point need some physio for your shoulder - depending on how many nodes they take out, but of all of the things I went through with my dx - the neck dissection was the least bothersome. They may give you an NG tube to feed you as I think the tonsils will hurt more than the neck dissection.

Tors is also good because I believe it minimizes the amount of damage and tissue they remove. Hopefully this will be it for you. But if you do have to go through rads and chemo there will likely be a 4-6 week time period where you will have time to heal and hopefully eat some of your favorite fatty foods. That's the time to really bulk up if you can. Try to read up on your dx - without scaring yourself.

worst case scenario - if you do have to go through rads and chemo they will likely put a feeding tube in to help with nutrition, and you must remember - eating and drinking will make it easier for recovery.

best of luck... and hugs.