Go over to For A-Bodies Only and send user Partsmonsta a private message. He is out of Orlando, FL. and did a tail panel, grill and head light bezels for a 68 Road Runner for a customer of ours. He did not paint them as per the customer request, but the polishing was very good. These were nice pieces to begin with, so like anything, the better the quality of the part, the better the finished product will turn out.
If you have the time and the attention to detail, polishing the trim can be done by yourself. It is a dirty job and you really have to pay attention to what your doing as the trim can quickly become a projectile.
When sending the parts out to be done, ask if the finished product is actually anodized or bright dip coated? Many of the trim restoration shops only straighten and polish the trim, others will detail it with paint. But very few shops actually anodize their work.
Also, depending upon your level of restoration and the attention of the details, the painting of the finished product will drastically affect the overall quality of the piece. The masking techniques, paint that is used can really impact the pricing and appearance of the finished product.