There are several kinds of sedations.
Moderate: IV Sedation - this is an IV in your arm and you could be conscious, unconscious, or somewhere in between!
Strong: General Anesthesia - this is where they have to make sure you have an airway and you are all the way out.
Now, with the IV and General, the same drugs that "knock you out" can depress your central nervous system, blood pressure, heart rate, etc etc. Obviously, if these systems are depressed too far, the patient will die. Fortunately for you, your oral surgeon has at least four years of training beyond MY four years of dental school that teaches him all the tricks of advanced life support. So don't worry!
However, MY biggest concern is this: You're going in TOMORROW and you have no idea what the risks are or if your'e even going to GET sedation??? This is inconceivable to me! Before they schedule the extraction appointment, they probably did a consult. The surgeon looks at your xray and decides the degree of difficulty involved and (should) explain the risks of the procedures as well as your options in terms of anesthetic and sedation, including all risks of these procedures. I've NEVER heard of anyone saying, "Oh, just decide the day of and we'll explain the risks then."
The fact that you're even asking the question has me a little concerned, unless they already went over all that and maybe you just weren't paying attention or you didn't read the consent form they should provide OR maybe just lost the paper...??
Anyway, good luck.
Sedation is better and easier than not, esp if your'e well insured!