Doctor's have rightly suggested you extraction because at this age your jaw has attained maximum size and getting braces might require extraction of your teeth....
During extraction you won't feel any pain as you will be given anesthesia. Only thing to be felt will be pressure due to application of instruments....For detailed info on tooth extraction procedure you can visit the link....http://www.identalhub.com/dental-what-is-simple-tooth-extraction-procedure-886.aspx