I had my wisdom teeth removed (all four at once, one of which was partially impacted) under general anesthesia, and I'm still here!
First and foremost, try not to think about the procedure. You're having it performed by a professional, who has performed this same procedure gazillions of times. It sounds painful but, frankly, if you look at the surface level of most surgical procedures, they all sound that way!
As for the x-ray: this is a necessary part of the procedure. The doctor needs to see where your wisdom teeth are, how impacted they are, and so on and so forth. I know I had to have x-rays performed by both my dentist and the surgeon who actually removed my wisdom teeth, both the day of the consultation and the day of the surgery. Not a single mysterious growth was found!
I'm going to be honest, though. Having teeth removed does ache once the procedure is over and the anesthesia has worn off. I have a very small jaw, and over the course of my life, I've had to have around 18 teeth removed purely because there was no room for them. You'll be sore afterwards. Chances are, you're going to have gauze stuffed in your mouth and you're going to experience swelling and numbness. This is normal! When I had my wisdom teeth removed, I looked like a chipmunk for about a week and I had to have icepacks on my face almost all the time to try and help with the swelling. Was it unbearable? Absolutely not. Annoying? Definitely. (Honestly, the worst part of having teeth removed is the salt water gargle.)
I don't remember much about the actual procedure because, again, general anesthesia. I remember talking to one of the nurses about living in Chicago and then, bam, out cold. I woke up when they moved me to the recovery room for a few groggy seconds, and then I was fast asleep again. When I woke up and was ready to leave, I had a chipmunk face, no pain, and a prescription for Vicodin. My recovery was so painless, I maybe took two of those, and I don't have an especially high pain tolerance.
Local anesthesia, however, is a different situation. You likely won't be able to feel most of the left side of your face. If you have cavities, and you've had cavities filled, then you were given a local anesthetic. If you experienced any pain at that time, be sure to mention that to the doctor performing your wisdom tooth surgery. Otherwise, numbness is, well, numbness! It's a total loss of sensation. If being awake during the surgery bothers you -- or, maybe not even awake, so much as being aware of the surgery happening -- then ask your doctor if it would be alright to bring your iPod/music player with.
Whew. I think that covers just about everything? Again, I just want to reemphasize that having your wisdom teeth removed is an incredibly common procedure! There's going to be some swelling and soreness associated with it, so have icepacks on hand. Be sure to discuss the local anesthesia with your doctor! I'm sure he'll be able to give you much better answers than I have regarding the pain and the procedure.