I'm sorry to hear of your circumstances. As for your concerns, surgery can usually provide a satisfactory outcome but its difficult to imagine just exactly what you are describing. Find a local surgeon to evaluate your concerns and I would suggest your GYN doctor. If its truly the labia, find out what technique is going to be employed and get a second opinion from a plastic surgeon so you can make the best choice for yourself. If its your introitus where its cut close through the perineum, a gynecologist would be suggested to repair that. And costs will vary by what is required to provide you the result you want.
It is important especially as a woman to feel comfortable during sexual intercourse and it is difficult to feel comfortable if you are too self conscious. It is impossible to say without an examination or at least a photo what exactly needs to be done. It is hard to give a cost as it is not really clear how extensive the procedure would be. For instance, could it be done under local anesthesia in an office exam room or would it require sedation in the operative suite. I would recommend that you find a plastic surgeon (you can even find one that doesn't charge a consultation fee) and let them evaluate you and give you a quote. You would leave the office knowing the extent of the procedure and the cost.
It sounds as if you have a torn introitis at the posterior aspect. This area can certainly be repaired. The muscle would need to be accurately repaired along with excision of any scar tissue. A complete exam and treatment plan can be obtained from a surgeon experienced in this type of surgery.
Unfortunately without an exam, it is difficult to know exactly what you would need done. I recommend consulting with a Plastic Surgeon in your area so you can get an accurate quote.