I think the pain was manageable but it was a long way from pain free. I am very glad I had the surgery and would do it again but my sister who had a TKR about 18 months before I did warned me that I'd be sorry I had it done for the first two weeks and then it gets better. I was never quite sorry I had it done but the first couple of weeks were rough at times. I consider a few weeks a fair trade off for several pain free years though. The hospital nurse told me i would not be pain free in the first few weeks - they aim for no higher than a 3 for pain for the first few weeks and I would say that was mostly accurate for me. Once in a while a 4 , sometimes a 2 or even occasionally a 1 while lying down or icing. Nothing unmanageable. I appreciated a realistic idea of what was coming.
You can do this! All of us were somewhere between stressed and out and out terrified before our surgeries. Somehow we got through. As the others have said, share your anxieties with the staff. You normally get a good handful of pills before they start anything else. They can certainly add any number of anti anxiety drugs, sedatives, etc. Just make them aware of your concerns. I'm pretty sure I had the IV needle in my elbow, not my hand but maybe that varies from hospital to hospital. I don't like needles in the hand either and i think I might have remembered that. You will get a preop check and a chance to voice all your concerns and they will make a plan for you that takes all that into account. Don't freeze up before you give them a chance to help you. I suspect it won't be as bad as you are imagining.