Once you get past the injections you are generally home free. The dentist will numb the nerves and tissue surrounding the impacted tooth prior to extraction. One item to note, is an impacted tooth sometimes requires the dentist to make deep injections so consider a mild over the counter pain relief medication in advance. In addition, make sure the topic ointment used to initially numb the gum tissue sits on the gums for a minute or two.
Finally, and most important please be sure to express any reservations you may have about the procedure to the dentist. You are paying for their service and they should be willing to sit with you for a few minutes and explain the extraction process and resolve an concerns you may have regarding the pain involved.