Usually they let you decide what type of abortion procedure you would like. Right now you have the choice between RU486 (a medication abortion) or a suction curettage. You can read more about the procedures here:
optionline.org/abortion.html
I think that it is not good that your doctor has not discussed this with you thoroughly. It's your body and your choice so you have a right to know what is going to happen when you have an abortion. If I were in your shoes I think I would reconsider this.
Abortion is a big deal and it is something that you should do with great caution. There are physical side effects and there are emotional ones. I would really like to encourage you to make an informed decision about your body and get all the facts before you go in for the procedure.
Here is the phone number for the website I linked to above. It's 1-800-395-HELP. They are a non-profit organization and they can discuss with you all of your options. It's free to call so you have nothing to lose. At the very least it will help you mentally prepare for your abortion.
Having an abortion is a decision that will change the rest of your life. Unfortunately, it's not like getting your wisdom teeth pulled. I have spoken with people who had abortions 30 years ago and they are still not over it. If you need to there is nothing wrong with calling your abortion clinic and moving your appointment to another date so you can think things over. You have to make the best decision for you and your body. Don't rush into it.