Hi Dizz_zzey,
For me, focussing on the practicalities helped. I kept working through in my mind that I have to have this operation, my surgeon has a lot of experience, the head and neck cancer support team were great with any questions , determinedly NOT looking at Dr Google till I was after it. For me, just working through these kind of steps in my head every time i got panicky really helped. I also got one of those meditation apps and worked through the free bit of it. I had left neck dissection but i wouldn't say it's "disfiguring"... I was offered NHS make up and camouflage sessions once it had healed, for my neck and for my arm where they'd operated to take the flap.
Obviously anxiety will probably increase as you get closer to the op date, but for me by the time it came to it, i just was raring to go and get it over with so I could start recovery.
Don't know if any of that will help you, its just my take on it, and I've been told I'm weird often enough.