Freakedout, there are others in this forum who can give you good relaxation tips and techniques. But I can describe what I went through when I had IV for a molar extraction.
IV really is a wonderful thing. I was a right physical and emotional mess when I got in the chair, but all that happens is (from my experience, that is), you go in, quickly weighed, a blood-pressure cuff is put on one arm, a cannula - which is a tiny little plastic needle - is put in a vein on the back of your hand (sometimes it can be inside your elbow), which is nothing more than a very, very, tiny little pinch and a syringe is slowly emptied into the cannula. I was told to sit back and relax. By the time I counted to ten, I was in the other room, tooth missing, full of LA and wondering "how did I get here?", "What just happened?" and "Who cares anyway?"
It really is nothing more than that. I felt nothing, I heard nothing and I remembered nothing. I just wanted to go home and sleep for the rest of the day.
Sometimes people can ask for a pill to take before going into the surgery, but in my case I didn't and its not always offered. I guess it depends on the surgery and where you are. Post operative care should be to warn about continual bleeding, stuff like don't spit out fluids or use drinking straws for the first 48hrs (there are dental professionals on here who may give the correct advice), don't get food in the socket, keep your head up and nighttime and gently rinse out your mouth with salt water every four hours.
As for pain, take some ordinary pain killers before the LA's wear off. It shouldn't be very painful, but it may be uncomfortable for a few days.
Believe me, when it comes to pain and anxiety, there cannot be many people worse than me!!! But the worst thing about IV - is sitting in the waiting room getting yourself in a state of panic about it. IV is the absolute best thing ever!!! It has changed my life with regard to having extractions.
Hope this helps