I would say please please please try a chiropractor before you have surgery. Botox will NEVER cure tremors or cervical dystonia, it will only essentially paralyze the muscles for a time until your body reacts and destroys the toxins. I'm not exactly sure about your nervous condition, but most of the time doctors don't provide anti anxiety medication through injection, it is typically orally administered, the same with the B12, which occurs naturally in foods as well. So I'll just focus on the cervical dystonia.
Chiropractors deal with the spine, and the nervous system which is essentially where your problems are coming from. Likely there is some type of nerve interference, which causes the dystonia, so until that interference is removed, you will constantly have problems. This interference can either cause a decrease in muscle tone, or an increase in tone. A chiropractor will be able to determine where that interference is and will be best able to determine whether or not they can assist, or if it is beyond their abilities. Be aware it may be a somewhat lengthy process as the condition didn't appear overnight, it can't be fixed overnight, surgery or not. If you have surgery, it is likely you will have other problems down the road either with restricted motion and/or decreased function beyond what you are currenlty experiencing. The spine was made to move, and your muscles to cause that motion, if you do something such as surgery to alter that, than your body will need to do something else to compensate, which is why further problems may develop. There are some extreme cases where surgery is the best route however, but I urge you to exhaust any other treatment possibilities before having surgery. Find a quality chiropractor in your area, who gets results. Best of luck.
In my 2nd year of chiropractic school, and I am a certified athletic trainer