It is more major surgery. When you have had radiation which has caused severe scarring a flap may be the only alternative. Whichever method is used, additional surgery is needed if you want to have the nipple and areola rebuilt. The scar from breast reconstruction depends on the method used. For expanders and implants no new incision is used because the original mastectomy scar is reopened.
All surgery requires a scar and all scars take time to soften and fade.
You will not see the final appearance of your scar for a year after surgery. It is usually red and raised for the first month or two after your operation. Most of the time this is an outpatient operation and a stay in the hospital is not needed. All operations have some risk. Your surgeon will explain the operation you choose in more detail.